DESIGN GUIDE A COUSTIC ACOUSTIC. Insulation Design Guide

Transcription

1 DESIGN GUIDE A COUSTIC ACOUSTIC Insulation Design Guide

2 Contents. Introduction 2 Product Range, Applications & Selection Guides 3 13 Bradford Acoustic Solutions Party & Interior Walls Residential & Commercial 14 External Walls 18 Roof/Ceiling Systems 18 Floor/Ceiling Systems 23 Floors 24 Plumbing 25 Gutters & Downpipes 26 Pipes, Tanks & Vessels 27 Factories & Workshops 27 Acoustic Baffles 29 Acoustic Enclosures 30 Vibration Damping 34 Air Conditioning Systems 36 Bradford Acoustic Solutions for Specialty Applications Home Cinema 46 Auditoriums 47 Sports Complexes 48 Canteens/Restaurants 50 Karaoke/Night Clubs 50 Shopping Centres 51 Recording Studios 52 Heavy Plant 53 OEM Application 53 Appendix A The Nature of Sound 54 Sound Transmission 57 Flanking Paths 59 Sound Absorption 59 Reverberation 61 Room Acoustics 64 Industrial Acoustics 67 Speech Privacy 68 Appendix B Floor/Ceiling Systems Appendix C Product Data 71 Sound Absorption Coefficients 74 Static Insertion Loss/Silencers 77 Air Flow Resistivity 78 Appendix D Terminology 79 CSR Bradford Insulation Regional Contact Details 80 Introduction. The Bradford Insulation Group forms part of the Building Materials Division of CSR Limited. CSR Bradford Insulation manufactures and markets an extensive range of insulation products offering outstanding thermal, acoustic and fire protection properties for use in all types of domestic and commercial buildings. Two mineral fibre insulation types are available; Bradford Glasswool, which is manufactured by controlled felting of biosoluble glass wool bonded with a thermosetting resin; and Bradford Fibertex Rockwool which is spun from natural rock and bonded with a thermosetting resin. Both are available in sheet or roll form and as moulded pipe insulation. Bradford Thermofoil and Thermotuff are a range of aluminium foil laminates available in various grades. All CSR Bradford Insulation products are tested to meet stringent quality control standards incorporating quality management systems such as AS3902/ISO9002. ABOUT THIS GUIDE. The purpose of this guide is to provide information on the technical benefits obtained with the inclusion of acoustic insulation materials in the construction of all types of buildings as well as noise control of machinery. The range of Bradford products and their applications is presented along with data and worked examples to illustrate design considerations. This Acoustic Design Guide also outlines the basic properties of sound, and methods for its control. It does not set out to provide a definitive solution to every conceivable noise problem. Rather, it aims to explain the principles involved, so that these principles can be applied along with common sense, to overcome common acoustic problems. Acoustics is however a complex science, and there will be many instances where the services of specialist acoustic consultants or noise control engineers are indispensable. The reader is cautioned against investing large sums of money in noise control without first seeking advice. This is particularly pertinent where compliance with noise abatement orders is concerned. TECHNICAL ASSISTANCE. To assist designers, a free and comprehensive technical service, as well as advice and assistance in specifying and using Bradford products is available from CSR Bradford Insulation offices in your region. Further technical data and product updates are also available on the CSR Building Solutions Website: Information included in this Design Guide relates to products as manufactured at the date of publication. As the CSR Bradford Insulation policy is one of continual product improvement, technical details as published are subject to change without notice. 2

3 The Importance of Acoustic Insulation. The minimisation of noise has become a significant environmental issue in the modern world, whether at home, at work or on holidays. CSR Bradford Insulation manufacturers and distributes an extensive range of insulation products that provide excellent noise control properties, as well as the traditional thermal and fire control benefits. Although all fibrous insulation products can provide some acoustic benefits, CSR Bradford Insulation has a range of products specifically designed and tested for the acoustic insulation market, including: ACOUSTIC INSULATION PRODUCT Bradford Glasswool Partition Batts Bradford SoundScreen Bradford ACOUSTICON Bradford Glasswool R1.5 ACOUSTITUFF Ductliner Bradford Glasswool R1.5 ULTRAPHON Ductliner Bradford ACOUSTICLAD Bradford Glasswool ACOUSTILAG Bradford FIBERTEX Acoustic Baffle Bradford Glasswool SUPERTEL Bradford Rockwool FIBERTEX 450 APPLICATIONS Economical insulation for internal wall sound absorption in housing, residential apartments or commercial offices. Various systems are available to meet building codes. Unique rockwool insulation system to reduce room-toroom noise transmission in houses. Commercial and residential metal roofing insulation specially developed to reduce rain noise. Air conditioning duct internal lining product offering full enclosure with excellent sound absorption properties. High performance acoustic absorption product for ducting, silencers and other acoustic applications. Wall absorber combining the superior acoustic properties of Bradford Fibertex Rockwool with a perforated metal panel system. Pipe insulation product combining the noise barrier properties of loaded vinyl and the absorption benefits of glasswool. Ideal for noisy plumbing. Rockwool batt enclosed in white polymer film used for which is designed to be hung from the overhead structure to provide acoustic absorption in a room or workplace. General purpose medium density glasswool acoustic insulation. General purpose premium rockwool acoustic insulation product. 3

4 Acoustic Insulation for Homes. 1Metal Roof Insulation or Tiled Roof Sarking 2Ceiling Insulation 3Internal Wall Insulation 4External Wall Insulation/ Party Wall 5Plumbing Insulation 6Acoustic Floor/Ceiling & Floating Floor Insulation 7Home Cinema Wall, Floor & Ceiling Insulation. Acoustic Absorbing Panels 4

5 1 Metal Roofing Tiled Roof Sarking 2 Ceiling 5 Plumbing 6 Acoustic Floor/Ceilings ACOUSTIC DESIGN GUIDE Bradford Insulation Application & Selection Guide for Homes. Insulation Application Product Type Product Range/Facings 3 4 Acoustic Internal Walls External Walls Bradford ACOUSTICON Blanket Bradford Glasswool ANTICON Blanket Bradford FIBERTEX Rockwool ANTICON Blanket Bradford THERMOFOIL Sarking Bradford THERMOTUFF Sarking Medium, Heavy Duty or Specialty THERMOFOIL R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL Medium, Heavy Duty, ANTIGLARE Medium, Extra Heavy Duty, Safety Bradford Glasswool Gold Ceiling Batts R2.0, R2.5, R3.0, R3.5, R4.0 Bradford FIBERTEX Rockwool Ceiling Batts R2.0, R2.5, R3.0 Bradford ACOUSTILAG Bradford Glasswool Partition Batts Bradford Rockwool SoundScreen mm Loose Fill Bags 50, 75 and 100mm 75mm Bradford Glasswool Gold Wall Batts R1.5, R2.0 Bradford FIBERTEX Rockwool Wall Batts R1.5, R2.0 Bradford FIBERTEX Rockwool Cavity Wall Granulated Loose Fill Bags Bradford ACOUSTILAG Pipe Insulation ACOUSTILAG 20, 23 and 26 Bradford HANDITUBE Pipe Insulation Bradford FIBERTEX Rockwool Ceiling Batts R1.5 - R2.0 Bradford Glasswool Wall/Floor Batts R1.5 - R2.0 Bradford FIBERTEX Rockwool Wall/Floor Batts R1.5 - R2.0 Bradford Rockwool SoundScreen Stocked by CSR Bradford Insulation 75mm Floating Floors Bradford Glasswool QUIETEL Specialty installation system 7 Home Cinema Bradford Glasswool SUPERTEL Bradford FIBERTEX Rockwool Specialty facings available 5

6 Acoustic Insulation for Homes. 1Tiled Roof Sarking or Metal Roof Insulation 2Ceiling Insulation 3Internal Wall Insulation 4External Wall Insulation 5Plumbing Insulation 6Acoustic Floor/Ceiling & Floating Floor Insulation 7Home Cinema Wall, Floor & Ceiling Insulation. Acoustic Absorbing Panels 6

7 1 Metal Roofing Tiled Roof Sarking 2 Ceiling ACOUSTIC DESIGN GUIDE Bradford Insulation Application & Selection Guide for Homes. Insulation Application Product Type Product Range/Facings Bradford ACOUSTICON Blanket Bradford Glasswool ANTICON Blanket Bradford FIBERTEX Rockwool ANTICON Blanket Bradford THERMOFOIL Sarking Bradford THERMOTUFF Sarking Medium, Heavy Duty or Specialty THERMOFOIL R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL Medium, Heavy Duty, ANTIGLARE Medium, Extra Heavy Duty, Safety Bradford Glasswool Gold Ceiling Batts R2.0, R2.5, R3.0, R3.5, R4.0 Bradford FIBERTEX Rockwool Ceiling Batts R2.0, R2.5, R3.0 Bradford ACOUSTILAG 25mm 50mm 3 4 Acoustic Internal Walls External Walls 5 Plumbing 6 Acoustic Floor/Ceilings Bradford Glasswool Partition Batts Bradford Rockwool SoundScreen 50, 75 and 100mm 75mm Bradford Glasswool Gold Wall Batts R1.5, R2.0 Bradford FIBERTEX Rockwool Wall Batts R1.5, R2.0 Bradford FIBERTEX Rockwool Cavity Wall Granulated Loose Fill Bags Bradford ACOUSTILAG Pipe Insulation ACOUSTILAG 20, 23 and 26 ARMAFLEX Pipe Insulation Bradford FIBERTEX Rockwool Ceiling Batts R1.5 - R2.0 Bradford Glasswool Wall/Floor Batts R1.5 - R2.0 Bradford FIBERTEX Rockwool Wall/Floor Batts R1.5 - R2.0 Bradford Rockwool SoundScreen Stocked by CSR Bradford Insulation 75mm Floating Floors Bradford Glasswool QUIETEL Specialty installation system 7 Home Cinema Bradford Glasswool SUPERTEL Bradford FIBERTEX Rockwool Specialty facings available 7

8 Acoustic Insulation for Commercial Buildings 7Air Conditioning Duct Insulation (Rigid & Flexible Ducts) 6Fan Silencer & Fan Casing Insulation 1Ceiling Insulation (Suspended Grid Ceilings & Concrete Roof/Soffit) 2Internal Partition Wall Insulation 3Acoustic Absorbing Panels 4Plumbing Insulation 5Plant Room Wall & Ceiling Insulation 8

9 Bradford Insulation Application & Selection Guide for Commercial Buildings. Insulation Application Product Type Product Range/Facings Bradford Glasswool ANTICON R1.5, R2.0, R2.5 Faced Light, and ACOUSTICON Blanket Medium, Heavy Duty or Specialty THERMOFOIL Bradford FIBERTEX Rockwool R1.5, R2.0 Faced Light, ANTICON Blanket Medium, Heavy Duty or 1 Concrete Specialty THERMOFOIL Roof/Soffit Bradford Glasswool SUPERTEL 25 75mm THERMOFOIL Facing Bradford FIBERTEX 350 Rockwool mm THERMOFOIL Facing Bradford Glasswool Ceiling Panel Overlays Factory Applied Acoustic Facings Exposed Grid Bradford FIBERTEX Rockwool Ceiling Ceiling Panel Overlays Factory Applied Acoustic Facings Bradford Glasswool Building Blanket R1.2, R1.5, R1.8, R2.0, R2.5 Concealed Grid Bradford FIBERTEX Rockwool Ceilings Building Blanket 50, 75mm, R1.5, R2.0 Acoustic Internal Bradford Glasswool Partition Batts 50, 75, 100mm 2 Partitions Bradford FIBERTEX Rockwool Partition Batts 45, 70mm 3 Acoustic Absorbing Panels Bradford Glasswool ULTRATEL Board mm, Factory Applied Facings Bradford FIBERTEX 450 Rockwool mm, Factory Applied Facings Bradford ACOUSTILAG Pipe Insulation ACOUSTILAG 20, 23 and 26 Plumbing Insulation ARMAFLEX Pipe Insulation Stocked by CSR Bradford Insulation Bradford Rockwool/Glasswool ACOUSTICLAD Plant Room Bradford Glasswool FLEXITEL, Perforated 750P Wall & Ceiling SUPERTEL, ULTRATEL THERMOFOIL Insulation Bradford FIBERTEX 350 Rockwool Perforated 750P THERMOFOIL Bradford Glasswool FLEXITEL Perforated 750P Bradford Glasswool SUPERTEL THERMOFOIL Fan Casings Bradford Glasswool QUIETEL ACOUSTITUFF Bradford FIBERTEX Rockwool DUCTLINER ULTRAPHON Bradford Glasswool SUPERTEL BMF, ULTRAPHON Bradford Glasswool ULTRATEL mm Fan Silencers Bradford Glasswool QUIETEL (Quietel 13mm - 50mm) Bradford FIBERTEX Rockwool DUCTLINER Bradford FIBERTEX 450 Rockwool Bradford Glasswool SUPERTEL Perforated 750P THERMOFOIL Rigid Ducting Bradford Glasswool DUCTLINER ULTRAPHON, Internal Lining Bradford Glasswool ULTRATEL ACOUSTITUFF facings Bradford FIBERTEX Rockwool DUCTLINER mm, R1.5 & R0.9 Bradford Glasswool MULTITEL R1.5 & R0.9 Rigid Ducting Bradford Glasswool FLEXITEL mm External Wrap Bradford Glasswool THERMOGOLD DUCTWRAP Bradford FIBERTEX Rockwool DUCTWRAP Bradford Glasswool R1.0 SPECITEL R1.0. R1.5 Flexible Duct Bradford FABRIFLEX Flexible Ducting Available ex-singapore Bradford ACOUSTIFLEX Flexible Ducting Available ex-singapore 9

10 Acoustic Insulation for Theatre, Sports & Multi-Purpose Buildings 1Auditorium/Theatre/Cinema Roof/Ceiling Insulation Wall Insulation Acoustic Absorbing Panels 2Sports Centre Roof/Ceiling Insulation Floor Insulation Acoustic Absorbing Panels 4Air Conditioning System Insulation 3Canteen Wall Insulation Ceiling Insulation Acoustic Absorbing Panels Metal Deck Rain Noise Insulation 10

11 Bradford Insulation Application & Selection Guide for Theatre, Sports & Multi-Purpose Buildings. 1 2 Sports Buildings Swimming Basketball Gymnasium 3 Canteen Facility 4 Theatre, Cinema & Auditorium Air Conditioning Systems Insulation Application Walls Acoustic Absorbers Roof/Ceiling Acoustic Absorbers Roof/Ceiling Acoustic Absorbers Walls Roof/Ceiling Product Type Bradford Glasswool Partition Batts Bradford Rockwool Partition Batts Bradford Glasswool FLEXITEL, SUPERTEL ULTRATEL with BMF (Black Matt Facing Tissue), ULTRAPHON or other specialty facing. Bradford FIBERTEX Rockwool Bradford ACOUSTICLAD Wall/Ceiling Absorber Bradford Glasswool ACOUSTICON Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Bradford ACOUSTICLAD Wall/Ceiling Absorber Bradford FIBERTEX Rockwool Bradford Glasswool FLEXITEL, SUPERTEL ULTRATEL with BMF (Black Matt Facing Tissue), ULTRAPHON or other specialty facing. Bradford Glasswool ACOUSTICON Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Bradford FIBERTEX Rockwool Bradford Glasswool FLEXITEL, SUPERTEL ULTRATEL with BMF (Black Matt Facing Tissue), ULTRAPHON or other specialty facing. Bradford ACOUSTICLAD Wall/Ceiling Absorber Bradford Glasswool Partition Batts Bradford Rockwool Partition Batts Bradford Glasswool ACOUSTICON Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Refer to CSR Bradford Insulation Air Conditioning Design Guide and Product Guide. 11

12 Acoustic Insulation for Industrial Applications. 2Acoustic Enclosures for Plant & Machinery 1Acoustic Baffles (suspended) 8Acoustic Wall Absorbers 7Metal Deck Roof Insulation 6Ceiling Insulation 3Bradford Insulation for OEM Applications 4Acoustic Absorbing Screens 5Acoustic Internal Wall Insulation 12

13 Bradford Acoustic Insulation for Industrial Applications. Insulation Application Product Type Product Range/Facings 1 Acoustic Baffles Bradford FIBERTEX Acoustic Baffle Fully enclosed in white polymer film ready to hang. 2 Acoustic Enclosures for Plant & Machinery Bradford FIBERTEX Rockwool mm Bradford Glasswool FLEXITEL Density kg/m 3 Bradford Glasswool SUPERTEL Bradford Glasswool ULTRATEL 3 OEM Applications Bradford Glasswool Appliance Grade Bradford Rockwool Appliance Grade Bradford Glasswool QUIETEL Cut to size with specialty facings available 4 Acoustic Absorbing Screens Bradford Glasswool SUPERTEL Bradford FIBERTEX Rockwool mm 5 Acoustic Internal Walls Bradford Glasswool Partition Batts Bradford FIBERTEX Rockwool Partition Batts To fit studs 6 Ceilings Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts mm 7 Metal Deck Roofs Bradford Glasswool ACOUSTICON Bradford Rockwool ACOUSTICON 75mm 8 Acoustic Wall Absorbers Bradford ACOUSTICLAD Bradford FIBERTEX Rockwool mm Specialty facings available 13

14 Bradford Acoustic Solutions. Interior Walls. RESIDENTIAL PARTY & INTERNAL WALLS. The Building Code of Australia (BCA) Sections F5 sets out Sound Transmission Class (STC) requirements for sound insulation of floors, walls, between units, walls between bathrooms, laundries, kitchens, between habitable and non-habitable rooms in multi-tenancy buildings. In late 1999, the BCA changed its acoustic rating from STC to Sound Reduction Index (R w ). This Acoustic Design Guide uses the STC rating units as Australasia and Asia are familiar with STC and it is very similar to R w. An increase of either one STC unit or one R w unit approximately equals a reduction of one decibel in noise level. Table 1 below shows common STC values of walls used in buildings. The expected audibility for a given STC level is also shown, based on guidelines for ambient sound levels TABLE 1. STC AND AUDIBILITY THROUGH WALLS AND FLOORS. STC Value Audibility Speech audible 40 Loud speech, still heard 45 Loud speech, just heard Speech cannot be heard The BCA Part F5.4 Sound Insulation Of Walls Between Units currently states a wall must have an STC not less than 45. It has been proposed to increase this to STC 55 in the future as STC 45 does not provide enough acoustic privacy. STC s 50 are standard in Europe and USA. Generally internal walls for residential applications in Australia use either rendered brick or lightweight double leaf walls using plasterboard and/or fibre cement construction on timber studs. To improve or increase the sound transmission loss (STL) hence the STC of these walls, the following is required:- EXTRA MASS. Sound Transmission Loss (STL) depends heavily on the surface density of a building element (mass per square metre of surface). For every doubling of surface density, the sound transmission loss increases by about 5dB. The addition of denser wall sheeting products such as CSR Gyprock Fyrchek or Soundchek plasterboard or CSR Fibre Cement together with Gyprock Resilient Mounts and furring channels can reduce noise levels. DOUBLE-LEAF WALLS. Higher transmission losses than those expected by the Mass Law can be obtained by using double-leaf walls with an air cavity. Further increases in sound transmission loss, particularly at low frequencies can be achieved by using wider air cavities. When a double leaf wall is uninsulated, the air in the cavity can act as a spring, efficiently transmitting sound energy from one side of the wall to the other. Significant improvement in STC is obtained by using Bradford Rockwool or Glasswool batts in the cavity. Acoustic tests of walls around the world have shown the use of glasswool batts or rockwool batts inside cavity walls reduces resonances between the two sheets and can significantly improve the acoustic performance by up to 10 STC. Generally the thicker and/or denser the insulation in the cavity, the higher the STC rating resulting in less noise transmitted to the other side of the wall. The actual improvement in STC depends on the type of wall construction. Insulation in the cavity will also lessen the effect of the coincidence dip in double leaf walls. FLANKING NOISE. It should be noted that actual installations, as compared to acoustic laboratories, exhibit flanking noise through doors, windows, ventilation ducting, air gaps at ceiling, wall and floor intersections. In addition, poor workmanship may degrade the acoustic performance of partitions. For these reasons, a building element constructed in the field will usually achieve a lower STC ratings than when tested in the laboratory. Maximum acoustic performance can be achieved by eliminating penetrations in walls, caulking gaps, and staggering electrical outlet or other necessary penetrations through the wall. Wall cavities should be completely filled with insulation and tightly fitted around pipes, conduits and other outlets. 14

15 LOW FREQUENCY NOISE. Low frequency noise from sources such as fans, aircraft, road and rail traffic, and bass from amplified music can penetrate walls easier than high frequency noise. Therefore higher sound transmission loss (ie. higher STC) walls are required to ensure satisfactory acoustic performance. As a general rule, add at least 5 STC points to the acoustic requirement of the walls when low frequency noise is present. STC data for some typical partition walls is given in Table 2. Further STC data for internal cavity walls is available the CSR Bradford brochure Noise Reductions For Internal Partitions or the CSR Gyprock Fire & Acoustic Design Guide, The Red Book. TABLE 2. STC DATA FOR TYPICAL TIMBER FRAME PARTITION SYSTEMS. Description STC (R w ) STC (R w ) STC (R w ) Bradford Bradford No Glasswool Rockwool Insulation Wall Batts Wall Batts STC layer 10mm CSR Gyprock Plasterboard CD 70/75mm Timber Studs 1 layer 10mm CSR Gyprock Plasterboard CD 42 SoundScreen (75mm Batts) (45mm Batts) Test CSR 37/67 STC layers 13mm CSR Gyprock Fyrchek plasterboard /75mm Timber Studs (50mm Batts) (45mm Batts) 1 layer 13mm CSR Gyprock Fyrchek plasterboard STC layers 16mm CSR Gyprock Fyrchek plasterboard x 35mm Staggered Timber Studs 2 layers 16mm CSR Gyprock Fyrchek plasterboard (50mm Batts) (45mm Batts) * Refer to the CSR Bradford Noise Reduction of Internal Partitions brochure or the CSR Gyprock Fire & Acoustic Design Guide ( The Red Book ) which show a wide range of internal partitions and their STC ratings. 15

16 COMMERCIAL INTERNAL PARTITIONS. Internal plasterboard or fibre cement walls using steel stud systems are widely used in commercial construction and offer a wide range of sound transmission loss performance. The methods stated previously for improving acoustic performance of Residential Internal Walls also apply to the Commercial Internal Partitions. Thinner gauge steel studs, with greater stud spacing and minimum fixing of sheets to studs also results in a wall which is able to flex more easily generally resulting in slightly higher acoustic performance. If higher STC performance is required, there are a number of steps that can be incorporated at the time of construction to improve acoustic performance, as detailed in Table 3. TABLE 3. INSULATION FOR NOISE REVERBERATION CONTROL. Addition STC Improvement Comments Fit insulation into studs Up to 10 STC points Thicker and/or denser insulation such as Rockwool is beneficial. Light gauge or deeper steel studs give higher STC performance. Use Gyprock Fyrchek Up to 3 STC points Use of 13mm or 16mm CSR plasterboard if installed both sides Gyprock Fyrchek improves performance due to extra mass. Gyprock Resilient Channel 6 8 STC points Resilient Channel isolate the one side Gyprock Plasterboard from the stud. Bradford Quietel one side and 4 STC points Quietel board acts as a sound insulation to stud isolator between the Gyprock Plasterboard and the Stud. Staggered and double studs Up to 10 STC points Provide sound breaks between solid studs and Gyprock. Recommended where impact isolation is also required. Gyprock Resilient Mounts and Up to 10 STC points Used where high level reduction of Furring Channel airborne and impact noise is required. 16

17 TABLE 4. STC RATINGS OF SOME COMMERCIAL INTERNAL PARTITIONS*. A sample of the STC ratings for commercial internal partitions using steel studs taken from the Tables in the CSR Bradford Insulation Noise Reductions for Internal Partitions brochure, together with results from recent testing. Description STC (R w ) STC (R w ) STC (R w ) Bradford Bradford No Glasswool Rockwool Insulation Partition Batts Partition Batts STC layer 13mm Gyprock Plasterboard CD (50mm Batts) (45mm Batts) 64mm Steel Studs Test HAS layer 13mm Gyprock Plasterboard CD STC layer 16mm Gyprock Fyrchek 64mm Steel Studs 1 layer 16mm Gyprock Fyrchek STC layer 13mm Gyprock Fyrchek plasterboard 64 x 0.75mm BMT Separated Steel Studs 1 layer 13mm Gyprock Fyrchek plasterboard STC layer 16mm Gyprock Fyrchek plasterboard 64 x 0.75 BMT Separated Steel Studs 1 layer 16mm Gyprock Fyrchek plasterboard STC layers 16mm Gyprock Fyrchek plasterboard 92 x 0.75mm BMT Separated Steel Studs 2 layers 16mm Gyprock Fyrchek plasterboard (50mm Batts) (45mm Batts) (75mm (75mm Wall Batts) SoundScreen ) (80mm Batts) (75mm SoundScreen ) (75mm Batts) (70mm Batts) * Refer to the CSR Bradford Insulation Noise Reduction of Internal Partitions brochure or CSR Gyprock Fire & Acoustic Design Guide ( The Red Book ) which show a wide range of internal partitions and their STC ratings. ACOUSTIC PREDICTION SYSTEM. CSR Bradford Insulation has available a sophisticated Acoustic Predictor computer program, developed by CSR Gyprock, which can predict the STC rating of many different internal partitions, in addition to those shown above and in the brochure. Note: For walls which require high sound transmission loss STC greater than 50, such as those used between recording studios or cinemas, flanking paths should be considered, as they can derate the acoustic performance of the partition. For cinema walls requiring a very high STC rating, contact CSR Bradford Insulation regarding the CSR Gyprock Cinema Wall System, or other CSR systems. 17

18 External Walls. External walls of residential buildings usually consist of brick veneer construction, or lightweight concrete construction, a cladding material, usually timber or fibre cement or occasionally double brick. For better acoustic performance, use building materials with more mass. Clay bricks provide high surface density (or mass per square metre) to enable high transmission loss. The use of CSR Gyprock Soundchek or Fyrchek plasterboard is recommended for interior walls. For even higher wall STC, the use of CSR Gyprock Resilient Mounts and Furring Channels is recommended. For brick veneer walls add the thickest possible rockwool or glasswool batts inside wall cavities during construction of the building. Granulated rockwool can be retro-fitted into existing walls of a building using a special machine which blows granulated rockwool under pressure into the wall cavities. Wall sheeting usually has solid connections (ie screw or nail fixed) to the timber or steel studs and transmits noise through these solid connections. CSR Gyprock Resilient Mounts can reduce both noise and vibration transmission. Gyprock Plasterboard FIG 1. EXTERNAL WALL INSULATION. Bradford Thermofoil or Thermotuff Breather Timber Frame Bradford Insulation Wall Batts External Cladding To improve STC performance of single timber studs, consider the use of Rondo resilient channels or CSR Gyprock resilient mounts with furring channels, which can improve STC (or R w ) by 6 to 8. Buildings with double brick walls should use vibration isolated wall ties to reduce the amount of noise and vibration transmitted from one wall to the other. Note that building elements of low acoustic performance will derate the improvements made to other building elements ie. walls and ceilings. For example, lightweight windows and doors can reduce the overall STC rating of the wall. Products. Bradford Glasswool Wall Batts Bradford Rockwool Wall and Ceiling Batts Roof/Ceiling Systems. Roof/ceiling systems generally consist of either steel roofing or tile roofing. These roofing systems usually provide average to poor acoustic performance and can be an acoustically weak link in a building facade. It should be noted that consideration should be given to other weak links in the building extensions such as windows and doors. Low frequency noise generated by aircraft, road and rail traffic can easily penetrate commonly used building materials including the roofing. Tile roofs are generally used in domestic applications. It is recommended that Bradford Rockwool or Glasswool Ceiling Batts be used in the roof cavity to improve both acoustic and thermal resistance. Note the higher the thermal resistance or R-value, the thicker the batt, and the better the acoustic absorption. The following points indicate methods to improve the acoustic performance of a typical tiled roof system. Tips on how to further improve the STC rating are provided in (brackets) Rockwool or glasswool insulation batts on top of the ceiling, (the thicker the insulation or the higher the R-rating, the better the acoustic absorption) Using a heavy THERMOFOIL sarking as a condensation barrier under the roof tiles, the heavier the better the noise reduction. Adding Bradford SOUNDLAGG loaded vinyl over the ceiling joists, (the heavier the better). Thicker and/or heavier plasterboard for the ceiling, (use fire rated plasterboard and multiple layers). Care should be taken to minimise all gaps in the roof ceiling to maximise the acoustic performance. 18

19 Figure 2 shows how to improve the acoustic performance of a typical tiled roof system. Note that the gaps inherent in tile roof construction allow noise to enter the roof cavity. Hence the use of TILED ROOF SYSTEMS. rockwool or glasswool insulation will maximise noise absorption in the roof space, minimising the amount of noise entering the room/s below. FIG 2. IMPROVING ACOUSTIC PERFORMANCE OF TILED ROOF SYSTEMS. Bradford Thermofoil 733 Sarking over rafters SYSTEM Monier concrete tile roof with one layer of Gyprock Supa-Ceil plasterboard fixed to ceiling joists spaced at 600mm centres. STC/R w 33 Monier Concrete Roof Tiles Bradford Soundlagg (6kg/m 2 ) over joists Add Bradford R2.5 Glasswool Batts between joists. 41 Replace Bradford R2.5 Glasswool Batts with Bradford R3.0 FIBERTEX Rockwool Building Batts between joists, and install Bradford THERMOFOIL 733 over rafters. 45 Ceiling Joist Add Bradford SOUNDLAGG (6kg/m 2 ) over ceiling joists. 50 Gyprock 10mm Supa-Ceil Plasterboard Ceiling Bradford Glasswool or Rockwool Ceiling Batts (as indicated) STEEL ROOFING SYSTEMS. Steel roofing is used in both commercial and residential roofing systems in Australia, New Zealand and Asia. Metal deck roofing systems require a layer of thermal insulation faced with a suitable vapour barrier to be installed directly underneath the metal decking to guard against condensation. Figure 3 shows the improvement in STC of a typical domestic roof with the addition of Bradford insulation in the roof/ceiling system. FIG 3. IMPROVING ACOUSTIC PERFORMANCE OF STEEL ROOF SYSTEMS. SYSTEM STC/R w Metal roofing with 1 x 10mm Gyprock Supa-Ceil plasterboard fixed to ceiling joists spaced at 600mm centres. 34 Bradford Acousticon Foil Faced Blanket Metal Roofing Add Bradford ACOUSTICON foil faced building blanket over rafters under metal roofing. 41 Add Bradford R2.5 FIBERTEX Rockwool Building Batts between joists. 45 Replace Supa-Ceil plasterboard with 2 layers x 13mm Gyprock Plasterboard CD fixed to metal furring channels (at 600mm max. cts) attached by Gyprock Resilient Mounts Metal roofing with one layer plasterboard fixed to ceiling joists spaced at 600mm cts. plus Bradford Ceiling Insulation between joist. (New Zealand only) Ceiling Joist Gyprock 10mm Supa-Ceil Plasterboard Ceiling Bradford Fibertex Rockwool Batts or (Bradford G lasswool Ceiling Insulation in New Zealand) 19

20 The STC of a roof system (commercial, industrial or domestic) can also be improved with the addition of heavier building materials such as: addition of insulation between the roof sheeting and Bradford batts above the ceiling, thicker steel roof sheeting, using heavier, fire rated plasterboard or multiple layers for the ceiling, installing a layer of Bradford SOUNDLAGG beneath (4 kg/m 2 or heavier). RAIN NOISE REDUCTION WITH METAL DECK ROOFING A common problem of steel roofing is that of rain noise, particularly in tropical climates with high levels of rainfall. Rain falling on metal deck roofing can cause unacceptably high noise levels in the space below the roof. The impact causes the stiff lightweight roof sheeting to vibrate, thus emitting noise. Damping the vibration of the roof sheeting reduces the emitted noise. Rockwool and glasswool blanket products have exceptional noise absorbing properties providing effective damping of the steel roof sheeting. CSR Bradford Insulation in conjunction with CSR Gyprock have constructed a rain noise testing facility to simulate rain noise using conventional 0.42mm thick BHP Trimdek Hi-Ten metal roof cladding. The rain noise test rig has four nozzles spraying water at high pressure simulate high intensity rainfall. Continuous noise levels of 89dB(A) were created inside the test rig, this noise level was used for controlled testing purposes. Figure 4 shows the rain noise insertion losses achieved by using Bradford Insulation Blankets faced with Thermofoil 729. All tests used 0.42mm BMT BHP Trimdek Hi-Ten steel roofing. FIG 4 RAIN NOISE REDUCTION INSERTION LOSSES FOIL FACED ROOFING BLANKETS. 50mm Bradford Rockwool Bradford ACOUSTICON Glasswool Roofing Blanket is faced with THERMOFOIL. ACOUSTICON has been specially developed to provide cost effective rain noise reduction of 18dB(A) insertion loss under metal deck roofing. ACOUSTICON has BHP approval for use under all types of Lysaght steel roofing profiles, including Klip-Lok. For more information refer to the Bradford ACOUSTICON A Quiet Step Forward brochure, available from your nearest Bradford office. For optimum rain noise reduction under steel roofing in commercial, industrial and residential applications, install 75mm Bradford ACOUSTICON. For residential applications, ensure the correct rating of thermal insulation is achieved for roof insulation in your region. At least R2.0 Bradford Rockwool or Glasswool Ceiling Batts should be installed between ceiling joists in conjunction with a Bradford ACOUSTICON. CSR Bradford Insulation and CSR Gyprock have conducted many tests using various foil faced roofing insulation blankets, ceiling tiles and fixed plasterboard ceilings. The results of these are shown in Table 5. In tropical climates, roofing insulation is generally installed foil face up, ie. the foil in direct contact with the metal deck roof sheeting. This reduces the insertion loss of the roofing blanket by 2dB. The use of Bradford Rockwool ACOUSTICON is therefore recommended. Rain noise tests were conducted using the same thickness/density glasswool blanket and varying the surface density of foil. It was found that the mass of the foil has no effect on the rain noise insertion loss achieved by the insulation. ACOUSTICON and ANTICON roofing blankets should be installed so the blanket is firmly in contact with the steel roofing as shown in Figure 5. This has the added benefit of damping the metal roof sheeting and reducing rain noise. FIG 5. REDUCTION OF RAIN NOISE METAL DECK ROOF. 75mm Bradford ACOUSTICON Optimum Metal Deck Roofing 50mm Glasswool blanket 50mm Polyester Blanket Bradford Acousticon Support Mesh (when specified) Bradford Thermofoil Vapour Barrier Purlin Insertion Loss db(a) 20

21 TABLE 5. NOISE REDUCTION CEILING SYSTEMS. Ceiling System Description Rain Noise Reduction Level db(a) Bradford ANTICON R1.5 Blanket hard under metal deck roof Bradford ACOUSTICON hard under metal deck roof Bradford FIBERTEX Rockwool ACOUSTICON hard under metal deck roof Rondo Suspended Concealed Grid Ceiling System. 1 layer x 13mm Gyprock Plasterboard CD. Bradford ANTICON R1.5 Blanket hard under metal deck roof Rondo Suspended Exposed Grid Ceiling System. CSR Gyprock Ecophon 20mm Lay-in Ceiling Tiles. Bradford ANTICON R1.5 Blanket hard under the roof. RONDO Suspended Exposed Grid Ceiling System. CSR Gyprock CELOTEX 16mm Lay-in Ceiling Tiles. Bradford ANTICON R1.5 Blanket hard under the roof. RONDO Suspended Exposed Grid Ceiling System. Gyprock 13mm Lay-in Ceiling Tiles. Bradford ANTICON R1.5 Blanket hard under the roof. RONDO Suspended Concealed Grid Ceiling System. 1 layer x 13mm Gyprock Plasterboard CD. Bradford ANTICON R1.5 Blanket hard under the roof. RONDO Suspended Concealed Grid Ceiling System. 1 layer x 13mm Gyprock Plasterboard CD. Bradford R1.5 GOLD BATTS or R1.5 Glasswool Building Blanket laid over the ceiling Bradford ANTICON R1.5 Blanket hard under the roof. RONDO Resiliently Mounted Suspended Concealed Grid Ceiling System layers x 13mm Gyprock Fyrchek Plasterboard. Bradford R1.5 GOLD BATTS or R1.5 Glasswool Building Blanket laid over the ceiling. Refer to the CSR Gyprock Fire & Acoustic Design Guide ( The Red Book ) for additional information on rain noise reduction ceiling systems. See comments regarding: Tropical climate applications in Bradford ACOUSTICON brochure. Products for Metal Deck Roofing Systems. Bradford Glasswool Acousticon 75mm. (R1.8) Bradford 50mm Commercial Grade Anticon. Bradford Glasswool R1.5 Anticon 55mm. Bradford Glasswool R2.0 Anticon 75mm. Bradford Glasswool R2.5 Anticon 95mm. Bradford 50mm Rockwool ACOUSTICON. CEILINGS. Fixed plasterboard ceilings generally provide better sound transmission loss (ie. higher STC) than lightweight suspended ceiling tiles and even plasterboard ceiling tiles. This is because the fixed plasterboard ceiling is better sealed and has less gaps. Multiple layers of plasterboard with resilient mounting and rockwool or glasswool batts in the cavity can provide high STC rating. The larger the ceiling cavity, the better the low frequency noise reduction. The ceiling can be an important area of a room to place sound absorption particularly, when the remainder of the rooms contains hard reflective surfaces. Rooms having no sound absorbent surfaces typically have high reverberation times. This results in poor acoustics, particularly if communication is required within the room. Generally commonly used plasterboard ceilings, whether fixed or lay in ceiling tiles are not very effective at absorbing sound. Typically, sound absorptive ceilings generally consist of: ceiling tiles made of high density rockwool or glasswool (typically NRC ), 21

22 perforated plasterboard or perforated metal pan ceilings with Bradford Rockwool or Glasswool insulation (faced with a black tissue) above (good sound absorption NRC ), Mineral fibre ceiling tiles (average sound absorption NRC ). Note that better low frequency acoustic absorption results when ceiling tiles are installed with an air cavity. The larger the air cavity, the better the low frequency acoustic absorption. In many commercial office buildings, noises such as conversations, telephones ringing etc can be heard from one office to another (also known as Crosstalk ). This can cause disruption, annoyance, and decreased productivity. Crosstalk usually occurs from sound flanking via the ceiling. In commercial office buildings, the walls are built up to the underside of the lightweight suspended ceilings (usually a metal grid), not to the concrete slab above. The lightweight ceilings tiles used generally have a low STC rating. The void above wall and ceiling allows sound to flank from one room to the next via the acoustically weak ceiling tiles. Ideally, the wall should be built up to the underside of the floor above without gaps for sound to pass from one side to the other. To reduce the amount of sound flanking when a wall does not continue to the underside of the floor above, it is recommended that Bradford Rockwool or Glasswool Ceiling Batts be installed between the wall/ceiling and the underside of the floor above. The more compressed the insulation is when installed in this way, the better the acoustic performance. refer to Figure 6. Alternatively, to reduce flanking via the ceiling, install Bradford Acoustilag from the underside of the concrete slab to the ceiling below as shown in Figures 7 and 8. FIG 6. IMPROVING SOUND TRANSMISSION CONTROL THROUGH CEILING AREA WITH BRADFORD INSULATION. Ducting Ducting Poor sound privacy caused by sound flanking through lightweight suspended ceiling Improved privacy with Bradford Rockwool or Glasswool Ceiling Batts in ceiling space over wall Bradford Rockwool or Glasswool Ceiling Batts compressed between ceiling and slab above Ducting Ducting Products - Ceilings. Bradford Rockwool Ceiling Batts R1.5, R2.0, R2.5, R3.0. Bradford Glasswool Ceiling Batts R2.0, R2.5, R3.0, R3.5, R4.0. Bradford Glasswool Ceiling Panel Overlays (optional Black Matt Facing, or ULTRAPHON ) Bradford Glasswool Absorption Blanket (optional Black Matt Facing or ULTRAPHON Bradford Fibertex Rockwool (optional Black Matt Facing or ULTRAPHON ) Ducting Cabling Bradford Rockwool or Glasswool Partition Batts NOTE: Care must be taken when passing cables through insulation material due to possible overheating. Consult your electrician for more details. 22

23 FIG 7. IMPROVING SOUND TRANSMISSION CONTROL THROUGH CEILING AREA WITH BRADFORD ACOUSTILAG CURTAIN. 100mm minimum Suspended ceiling tiles/plasterboard C-track or timber batten fixed to soffit Bradford Acoustilag curtain continuous in ceiling area 250mm minimum FIG 8. JOINTING A BRADFORD ACOUSTILAG CURTAIN. 75mm Bradford Reinforced Aluminium Tape 50mm min. overlap Bradford Acoustilag curtain PENETRATIONS THROUGH BRADFORD ACOUSTILAG CURTAIN. Cut Bradford Acoustilag curtain to allow installation around pipes, ducting etc. A tight fit should be maintained to ensure acoustic integrity Floor/Ceiling Noise Control Systems. Multi-storey buildings with hard flooring such as timber, parquetry or tiles etc., can efficiently transmit both airborne and impact noise (structure borne vibration) to the rooms below if appropriate techniques are not incorporated at the time of construction. Installing carpet and underlay on the floor can significantly reduce the impact noise to the room below. Installing R2.0 or greater, Bradford Rockwool or Glasswool batts between the floor joists will reduce airborne noise by approximately STC 4 6. At the time of printing this guide, The Building Code Of Australia (BCA) Sound Insulation of Floors Between Units stated a floor separating sole occupancy units must have an R w of not less than 45. (Note: R w 45 approximately equals STC 45). Floors must also provide insulation against impact generated sound. It should be noted that STC 45 is not always adequate in reducing airborne sound through floors and walls. For better acoustic privacy, it is preferable to use a higher rating of say R w 50 or preferably R w 55. RETRO-FIT OF VIBRATION ISOLATED FLOOR. To reduce impact noise transmission through floor/ceiling systems on existing timber, concrete or tiled floors, a floating floor can be constructed on top of the existing floor. The floating floor should use a resilient damping material. Dense Bradford Rockwool, Glasswool or rubber materials can be used but care is needed to choose a material with the correct stiffness for the application and static load. The services of an acoustic consultant should be engaged to solve floor impact noise problems and for the design of floating floors. Floating floors should not be mechanical fixed (nailed or screwed) to the existing floor as this will couple the two floors resulting in very little damping. The resilient material should also be used between the edges of the floating floor and the walls of the building. Skirting boards should also be isolated or separated from the floating floor. Note the floor/ceiling and floor/door heights may be affected by the use of a floating floor. Doors may also need undercutting if a floating floor is retro-fitted. Therefore where clearances are important, the floating floor height should be kept to a minimum. 23

24 REDUCING NOISE TRANSMISSION THROUGH TIMBER FLOOR/CEILING SYSTEMS. 1. Fit Bradford R2.0 (or greater) Floor Batts, or Rockwool/Glasswool Ceiling Batts tightly between ceiling joists. 2. Fix one layer of 13mm or 16mm Gyprock Fyrchek plasterboard to furring channels. 3. For better acoustic performance (to reduce airborne noise), choose a ceiling with more mass ie. multiple layers of Gyprock plasterboard CD or Gyprock Fyrchek plasterboard. 4. CSR Gyprock Resilient Mounted Furring Channels will further improve acoustic performance as well as impact isolation. 5. To improve impact isolation of floors, use carpet and good quality thick underlay over timber flooring. REDUCING NOISE TRANSMISSION THROUGH CONCRETE FLOOR/CEILING SYSTEMS. For concrete floor ceiling constructions, use vibration isolated ceiling hangers or resiliently mounted furring channels to support the plasterboard ceiling. Products. Bradford Floor Batts. Bradford Glasswool R2.0, R2.5, R3.0, R3.5, R4.0 Ceiling Batts. Bradford Rockwool R1.5, R2.0, R2.5, R3.0 Wall/Ceiling Batts. Bradford Glasswool Quietel (for impact isolation). FIG 10. TYPICAL METHODS FOR IMPROVING ACOUSTIC PERFORMANCE OF A CONCRETE FLOOR/CEILING SYSTEM. Carpet and underlay FIG 9. TYPICAL METHODS FOR IMPROVING ACOUSTIC PERFORMANCE OF A TIMBER FLOOR/CEILING SYSTEM. SYSTEM 19/20mm Timber Flooring, 200 x 50 Timber Joists at 450mm centres, 1 layer x 13mm Gyprock plasterboard CD. Add Bradford R2.0 GOLD BATTS between joists. Add Gyprock Resilient Mounts and Furring Channels at 600mm centres between joists and plasterboard. Add Carpet and Underlay. Add second layer of 13mm Gyprock plasterboard CD STC/R w Carpet and underlay Timber flooring Bradford Glasswool or Rockwool Insulation Timber joists Furring channel Gyprock resilient mount Use higher density Gyprock plasterboard (Soundchek or Fyrchek) and/or multiple layers A large range of floor/ceiling systems incorporating alternative acoustic upgrades is detailed in Appendix B of this publication. Refer to the CSR Gyprock Fire & Acoustic Design Guide The Red Book for additional information on floor/ceiling systems Concrete slab floor Bradford Rockwool or Glasswool Insulation Suspended ceiling system Gyprock resilient mount Furring channel Higher density Gyprock plasterboard (Soundchek or Fyrchek) and/or multiple layers Floors. Improved air-borne sound reduction and impact isolation can be achieved by using floating floors as shown in Figures 11, 12 and 13. High density, resilient Bradford Rockwool or Glasswool Quietel can break the sound and vibration transmission paths while having sufficient compressive strength to support the floating floor and the room contents. Vibrational energy is absorbed in the resilient material rather than transmitted to the building structure. Not only does a floating floor achieve effective structureborne sound control, but it also reduces the air-borne sound transmission to and from the room below. The Bradford Fibertex Rockwool or Glasswool Quietel board are laid flat on the floor, ensuring all joints are tightly butted. At the edges of the rooms, the batts continue up the walls. For the concrete floor, waterproof film is then used to cover the batts and a concrete screed floor of suitable thickness is poured. 24

25 All equipment is then mounted on the screed floor which is acoustically isolated from the main building structure. FIG 11 TYPICAL FLOATING FLOOR TIMBER OVER CONCRETE. Timber battens Plywood Sheeting Particleboard or timber board flooring Bradford Fibertex Rockwool or Glasswool Quietel Structural floor Air gap at wall FIG 12 TYPICAL FLOATING FLOOR CONCRETE OVER CONCRETE. 50mm Concrete Wire mesh Bradford Fibertex Rockwool or Glasswool Quietel Floor finish Structural floor Waterproof film FIG 13 TYPICAL FLOATING FLOOR TIMBER OVER TIMBER JOIST CONSTRUCTION. Timber flooring Gyprock plasterboard ceiling Plywood sheeting Bradford Quietel Board Plywood sheeting Bradford Glasswool/Rockwool Ceiling Batts NOTE: The upper plywood layer should not be nailed or screw fixed to the timber below. Instead, it should float on the base floor to effectively damp vibration. The floor should also be isolated from the walls. CSR Bradford Insulation recommends consulting an acoustic engineer for the design of floating floor systems. VIBRATION RESISTANCE. As Bradford Fibermesh Rockwool is stitched to wire mesh, the blankets are especially resistant to fallout under conditions where vibration is present. Bradford Fibermesh is particularly suitable for applications involving both vibration and high temperature where standard bonded insulation materials are less resistant to the effects of vibration. Products. Bradford Glasswool QUIETEL. Bradford FIBERTEX HD Rockwool. Bradford FIBERTEX HD (High Density) Rockwool. Bradford FIBERMESH Rockwool. Plumbing. Noisy pipe work is a common problem in many buildings. These days, pipe work building trends commonly use inexpensive, lightweight, easily to install materials with thin wall thicknesses which are unacceptably noisy. Offices, hotels, apartments and domestic houses can all benefit from reduced soil and waste pipe noise levels. Designers, hydraulic consultants, engineers, plumbers, owners and occupants of buildings should all take steps to insulate pipes and ducts to reduce noise. Water flowing through commonly used PVC soil and waste pipes is predominantly high frequency noise. To effectively reduce pipe noise, lag the pipes with Bradford Acoustilag 20, 23 or 26 pipe insulation. The 20, 23, and 26 indicate the A-weighted [db(a)] insertion loss achieved by lagging PVC pipes with each of the Bradford Acoustilag product respectively. (Refer to Appendix B for additional information). Note, the 20, 23 and 26dB(A) insertion losses only apply to water flowing through PVC pipes which have been correctly lagged with Acoustilag. Using Acoustilag for lagging other noise sources, eg., a fan casing or sheet metal air ducts, will generally result in lower insertion losses to those quoted, as these noise sources have more low frequency noise energy. To achieve the insertion losses quoted, Bradford Acoustilag should be installed with all joins of the lagging overlapped or butted, tightly and taped with Bradford 493 reinforced foil tape. Minimising all the gaps increases the acoustic performance of the lagging. The Building Code of Australia (BCA) states that: Soil and waste pipes are to be separated if a soil or waste pipe, including a pipe that is embedded in or passes through a floor, serves or passes through more than one sole-occupancy unit: 25

26 (a) The pipe must be separated from the rooms of any sole-occupancy unit by construction with an STC not less than: (i) STC 45 if the adjacent room is a habitable room (other than a kitchen); or (ii) STC 30 if the adjacent room is a kitchen or any other room. The Bradford ACOUSTILAG Pipe Insulation brochure provides systems using CSR Gyprock plasterboard to achieve the STC noise criteria specified by the BCA. The STC 50 system specified in that brochure is intended for applications requiring better acoustic isolation from waste pipe noise than is specified in the BCA eg., board rooms, offices, apartments and hotels etc. To achieve the STC s specified in Table 6, it is imperative that the pipes be correctly lagged (no gaps to allow noise leakage), and the plasterboard ceiling and walls above be airtight with no gaps into the next room. It is recommended the services of an acoustic consultant or acoustic engineer be used to achieve specified STC ratings. Penetrations, ducting, light fittings, gaps in ceilings etc., can degrade the acoustic rating of the lagging and ceiling system. To minimise annoyance from plumbing noise, it is advisable, at the design stage, to avoid placing bathrooms and laundries etc., adjacent to noise sensitive areas. Methods for minimising plumbing noise include: Select vibration isolated pipe hangers to support pipes and minimise transmission of vibration into the building structure. These will reduce water hammer noise when turning the water taps on or off. Alternatively use ARMAFLEX insulation between pipes and the building structure. Use water supply and drain pipes that are oversized, this may reduce line pressure and minimise flow noise. Where possible, use cast iron waste water pipes in place of lightweight plastic pipe to substantially reduce plumbing noise. The heavier, stiffer walls of cast iron pipes effectively reduce noise. If plastic waste water pipes must be used, use Bradford ACOUSTILAG to effectively reduce noise. Insulate all pipes and plumbing that are chased into brick walls. Select quieter plumbing equipment and appliances eg. cisterns, washing machines, clothes dryers etc. Products. Bradford ACOUSTILAG 20, 23 or 26. Bradford 493 reinforced foil tape. ARMAFLEX insulation. Quietening Box Gutters & Downpipes. Box gutters should be insulated with Bradford FLEXITEL or SUPERTEL Glasswool (25mm thick) faced with heavy duty foil. Insulation can be attached to gutters using 45mm long Bradford self-adhesive fasteners and washers at 300 mm centres. Insulation should be held firmly against the metal surface for maximum dampening. For better noise reduction, use Bradford ACOUSTILAG 20. Noisy downpipes should be insulated with Bradford Glasswool Sectional Pipe Insulation faced with Heavy Duty Thermofoil. Alternatively a 25mm wall thickness ARMAFLEX pipe insulation or Bradford ACOUSTILAG 20 can be fitted around downpipes. Products. Bradford Glasswool FLEXITEL or SUPERTEL. Bradford ACOUSTILAG 20. TABLE 6. ACOUSTIC INSULATION SYSTEMS FOR PLUMBING. System STC/R w Bradford CSR Gyprock Bradford Nº Rating. ACOUSTILAG Plasterboard Insulation BAS ACOUSTILAG 20 1 layer 10mm Nil Gyprock CD BAS ACOUSTILAG 20 2 layers 13mm CSR 75mm Bradford Gyprock CD Glasswool R1.5 BAS ACOUSTILAG 23 2 layers 10mm CSR 75mm Bradford Gyprock CD Glasswool R1.5 BAS ACOUSTILAG 23 2 layers 13mm CSR 100mm Bradford Gyprock CD Glasswool, R2.0 BAS ACOUSTILAG 26 2 layers 13mm CSR 75mm Bradford Gyprock CD Glasswool R1.5 Refer to the Bradford ACOUSTILAG brochure for additional information. 26

27 Insulation Cladding of Pipes, Tanks & Vessels. The insertion loss achieved by cladding pipes, tanks and vessels will depend on a number of factors such as the frequency of the fluid in the pipe the type and mass of the cladding material, the thickness and density of the (rockwool or glasswool) insulation. It should be noted that some of these cladding systems can actually amplify the noise at lower frequencies, particularly if insulation with a high density is used. This generally happens as the tank now has a larger radiating surface. Therefore it is difficult to predict the insertion loss of cladding systems. It should be noted that Bradford Rockwool or Glasswool SPI (sectional pipe insulation) will reduce pipe noise but not as effectively as Bradford ACOUSTILAG or insulation with a mass barrier. Higher density, means it is less resilient than Bradford ACOUSTILAG and more efficiently transfers noise and vibration from the pipe to the cladding/barrier. Note: Bradford ACOUSTILAG is not recommended for high temperature applications. Refer to the CSR Bradford Industrial Insulation Design Guide for installation details of cladding and pipe lagging. Factories & Engineering Workshops. The basic methods by which industrial noise may be controlled are: Sound absorption absorbing the noise using mineral fibre materials which can dissipate the sound energy as heat. Sound insulation (enclosing) containing the noise in one area so that it does not cause annoyance in other areas. Vibration damping damping vibrating surfaces to reduce air borne sound emission. Vibration isolation preventing acoustic energy from entering the building structure. These processes are illustrated in Figure 14. As the figure shows, treatment of a factory noise problem often involves a combination of the basic processes. FIG 14. BASIC NOISE CONTROL METHODS. Absorbent Lining reduces sound level within enclosure Vibration Damping of fan casing reduces sound emission Insulation reduces sound flow to outside Vibration Isolation Mounting reduces vibration transmission to floor REVERBERATION CONTROL. Factories and engineering workshops usually are reverberant spaces due to the lack of sound absorption within the space. Areas with multiple noise sources, such as factories, engineering workshops, bottling plants, machine halls, plant rooms etc usually have a high level of reverberant noise often exceeding the safe regulatory noise level of 85dB(A). The use of sound absorbing materials (such as glasswool and rockwool) to reduce reflected or reverberant sound is the most effective means of reducing overall sound levels in enclosed areas. CSR Bradford Insulation manufacture a range of rockwool and glasswool products with outstanding sound absorption properties. These products have been tested in acoustic reverberation rooms to determine the sound absorption coefficients presented in the technical data section. A range of factory-applied facings is available, the most common being: black fibreglass tissues (BMF), or ULTRAPHON THERMOFOIL laminates (solid and perforated). An extremely effective acoustic absorber for walls and ceilings is Bradford ACOUSTICLAD a roll formed panel, factory lined with Bradford FIBERTEX 350 Rockwool. Each panel interlocks with its neighbour forming a structurally reinforced joint. Bradford ACOUSTICLAD offers excellent test results with NRC ranges from 0.9 to Contact CSR Bradford Insulation for a brochure or refer to Appendix C for the Bradford ACOUSTICLAD absorption coefficients in 1 / 3 octave bands. 27

28 TABLE 7. ACOUSTICLAD TEST RESULTS. Acousticlad Test Sample Configuration Noise Reduction Perforated Coefficient % Open Area NRC Rating 15% 50mm thick Bradford FIBERTEX 350 Rockwool (60kg/m 3 ) Insulation with black matt facing (BMF) 1.00 between the Rockwool and Acousticlad face. 25% as above % as above % 23mm thick Mylar film between unfaced Bradford FIBERTEX 350 Rockwool and ACOUSTICLAD 0.90 perforated aluminium. 15% 50mm thick Bradford FIBERTEX 350 Rockwool Insulation with black matt tissue between the Rockwool and perforated aluminium. Timber spacers 1.05 supporting panels with average air gap 30mm. Notes All acoustic tests were conducted with ACOUSTICLAD perforated aluminium panels (0.7mm thick), with Bradford 50mm thick FIBERTEX 350 Rockwool (60kg/m 3 ) insulation. Acoustic tests were conducted in the reverberation room at the National Acoustic Laboratories, Chatswood, Sydney, Australia. See Appendix C for absorption coefficients at each 1 / 3 Octave band frequency. Bradford ACOUSTICLAD perforated metal is available with percentages of open area ranging from 10% to 55% and in a number of finishes including: galvanised steel, powder coated steel, stainless steel and aluminium. Fixing details for Bradford ACOUSTICLAD are available from your nearest Bradford office. Bradford Rockwool and Glasswool insulation is available with a range of facings, including: perforated metal or expanded metal. perforated foils, pegboard, wire, plastic mesh. Any perforated sheet facing should have an open area greater than 10% to maximise acoustic absorption. Other common methods for acoustic wall treatment involve: fixing timber battens or steel furring channels or Z sections at a spacing to suit the facing sheets. Bradford Rockwool and Glasswool batts are cut to size if necessary and friction fitted between the supports. The protective facing (e.g. perforated or expanded metal, plastic mesh, pegboard, wire etc.) is fixed to the furring sections or battens by nails, screws, or rivets as appropriate. Cover strips are used to improve the appearance. A commonly used cost effective method for fixing insulation (generally faced with perforated foil) on walls and ceilings uses drive pins and speed clips. These eliminate the need for battens or furring channels. The drive pins are fixed to the wall usually at 450mm centres. The insulation is pushed through the pins and held onto the pin by the speed clips of a suitable size. Rigid facings such as perforated metal or pegboard are unsuitable for this application method. The advice of adhesive suppliers should be sought before using adhesively fixed pins in lieu of drive pins. Ceilings may be lined by the same methods as walls. An alternative approach is to use a fully exposed metal suspension grid which makes it a simple matter to achieve any air gap required behind the batts Factories contain noise which predominantly has most energy at low frequencies which is difficult to absorb unless very thick insulation is used. To increase the low frequency sound absorption of perforated noise absorbers (such as Bradford ACOUSTICLAD ), introduce an air gap behind the insulation. This can be achieved by using larger battens or furring channels with chicken wire to retain the batts in position, as shown in Figure 15 below. Better acoustic absorption results when the depth of the air cavity is at least as thick as the insulation. Alternatively, rockwool or glasswool insulation greater than 75mm can be used with acoustically transparent facings mentioned above. 28

29 FIG 15. ABSORPTIVE LINING WITH AIR GAP TO BOOST LOW FREQUENCY ABSORPTION (PLAN VIEW). Chicken wire Structual wall Air gap FIG 16. BRADFORD ACOUSTIC BAFFLES USED TO ABSORB SOUND FROM NOISY EQUIPMENT. Bradford Fibertex Batts Facing eg. perforated metal Battens Products. ACOUSTICLAD with perforated metal facing is available in various thicknesses and open area percentage to accommodate acoustic absorption requirements. The following Bradford products can also be used: Bradford Rockwool FIBERTEX 350, 450. Bradford Glasswool FLEXITEL, SUPERTEL, ULTRATEL with perforated metal, expanded metal, wire, meshes or perforated heavy duty grade foil facings. Bradford Acoustic Baffles. Large factories or buildings may need a greater area of acoustic absorbing insulation than just the wall area, or may need it concentrated in a particularly noisy section of the building. Bradford Rockwool Acoustic Baffles may be suspended in any desired pattern to achieve extra sound absorption in a building. Refer to Figure 16 and 17. Sound absorption coefficients of Bradford Rockwool Acoustic Baffles are shown in Table 8. BAFFLE INSTALLATION. Two popular methods of installation are detailed. Baffles may be installed at any height, and do not need to be all in the same plane. A regular pattern such as parallel rows or a staggered, cross-hatched pattern is most easily installed using a suspended ceiling grid. Determine the number of acoustic baffles to be installed to meet the noise reduction required. The typical number of baffles is 1 baffle per square metre of ceiling area. Allowance should be made for lights and sprinklers. Installation Method 1. The baffles can be individually suspended from the roof structure using S hooks, galvanised wire or fine chain. In this case, suspend baffles approximately 1 metre below the ceiling level if possible. FIG 17. ACOUSTIC BAFFLES SUSPENDED AND ARRANGED IN A CROSS-HATCH PATTERN. Roof framing Suspension wire or chain 'S' Hook Bradford Acoustic Baffles in cross-hatch pattern TABLE 8. SOUND ABSORPTION COEFFICIENTS OF BRADFORD ACOUSTIC BAFFLES. Product Density Thickness Facing Frequency (Hz) (kg/m 3 ) (mm) NRC Bradford Acoustic Baffle µm plastic film 29

30 Installation Method 2. Inverted 50mm x 12mm aluminium U-channels are fixed to the underside of a ceiling grid. The baffles are then secured to the U-channel using self tapping screws. FIG 18. ACOUSTIC BAFFLES FIXED IN ALUMINIUM TRACK AND ARRANGED IN A PARALLEL PATTERN. Main suspension grid Aluminium channel Bradford Acoustic Baffles arranged in parallel pattern Products. Bradford Rockwool Acoustic Baffles. Acoustic Enclosures. Enclosures are an effective method of reducing noise emitted from a particular machine or noise source. They should be constructed of solid materials such as bricks, sheet steel, timber, plasterboard etc. Enclosures reduce noise more effectively when they are airtight, with no gaps or openings. This is not always possible as the machinery inside may need to be accessed by other machines or people, or require air flow for cooling. Enclosures built around machinery actually concentrate the noise inside the enclosure. Therefore it is good practice to line the inside of enclosures with Bradford Rockwool or Glasswool to reduce reverberant noise levels inside. A simple acoustic enclosure is shown in Figure 19. It has three main components: (i) an internal lining of sound absorbent rockwool or glasswool insulation to reduce the noise level inside the enclosure. (ii) a heavy barrier to reduce sound transmission to the outside. (iii) a resilient pad of felt or rubber to isolate the enclosure from the floor (optional). Broadly speaking, the sound transmission loss of an enclosure improves by about 5dB for every doubling of the surface density (mass per square metre or kg/m 2 ). Thus, a 2mm thick sheet steel enclosure will reduce the noise level by about 5dB more than a 1mm sheet steel enclosure, assuming all other conditions are equal. Enclosures do not attenuate all frequencies of sound equally, so the transmission loss achieved will depend on the frequency spectrum of the noise source. High frequency noise is more easily attenuated than low frequency noise. Thus, while a lightweight enclosure may provide effective transmission loss for a high frequency noise source, it could however be inadequate for low frequency noise sources. Flanking transmission paths permit sound to by-pass the acoustic enclosure. Typical examples are air gaps, windows, doors, service penetrations etc. To avoid severe reductions in insulation performance, steps should be taken to eliminate these flanking paths as far as practical. Caulking of air gaps and penetrations, use of door seals or even double doors, resiliently mounted double glazing, use of flexible couplings on pipes and ducting which penetrate the enclosure are all means of reducing flanking transmission. Flanking through the floor of an enclosure can limit the transmission loss. Sound and vibration entering the floor on the noisy side of the enclosure can be re-radiated to some extent on the other side. The sound insulation performance of lightweight enclosures may be significantly improved by the use of double-leaf construction with a core of sound absorbing rockwool or glasswool as shown in Figure 20. The performance will be further enhanced if the two leaves are of different surface densities eg: one leaf may be 1.6mm steel sheet while the other is 1.2mm steel sheet. This reduces resonant coupling between the sheets. The sound reduction achieved depends on the surface density of the enclosure. Heavy materials like steel sheet greater than 1.0mm, 16mm plywood or 19mm particle board are typically used. As well as trapping sound, enclosures of the type shown in Figure 19 and 20 will also trap heat. It is often necessary therefore to ventilate these enclosures to avoid overheating of the enclosed machinery. Ventilation openings must also be acoustically treated to reduce the escape of sound through these openings. The use of packaged attenuators, insulation lined ducts or acoustic louvres are commonly used. Absorptive treatment may include not only lining the walls and ceiling of an enclosure but also the use of discrete screens or baffles. The latter are of particular value where it is important that the absorptive treatment does not interfere with the dissipation of heat. Where heat could cause a problem, then Bradford Rockwool Acoustic Baffles are specially designed for suspension below existing 30

31 Bradford Fibertex 450 Rockwool or Ultratel ACOUSTIC DESIGN GUIDE FIG 19. ACOUSTIC ENCLOSURE. Heavy Gauge Steel Sheet factory roofs. Their sound absorption performance is detailed in the previous section. Baffles will not however be as effective at reducing noise as an enclosure. An example of an acoustic enclosure for very high acoustic insulation is detailed in Fig 21. It shows a room within a room. These rooms are vibration isolated from each other. Bradford Fibertex 450 Rockwool or Ultratel FIG 20. ACOUSTIC ENCLOSURE WITH DOUBLE-LEAF CONSTRUCTION. Heavy Gauge Steel Sheet Rubber Mounting Rubber Mounting INSTALLATION DETAILS. Installation of the sound absorbing rockwool or glasswool batts to the inside surfaces of the enclosure proceeds in a similar manner to that previously described for reverberation control. Where double-leaf construction is employed a larger number of variations are possible. One simple yet effective procedure follows: Construct a suitable frame using steel angles, channels, or box sections to provide at least 63mm clearance between the two leaves. (Note the wider the cavity, the better the low frequency sound transmission loss). Mount this frame on a continuous thick rubber mat. The outer steel sheeting should then be fixed to the frame as shown in Figure 21, using rubber strips to reduce sound transmission from the frame to the sheet. FIG 21. ACOUSTIC ENCLOSURE WITH VERY HIGH ACOUSTIC INSULATION. Minimum cavity of 200mm Heavy duty flexible pipe connection, and resilient mounted pipe/ductwork Bradford Insulation Blanket Two steel soundproof doors with all edges sealed Existing window Small double glazed viewing window Bradford Insulation Blanket in cavity Main structure of building Resilient/floating floor system 31

32 Fix 50mm thick FIBERTEX R350 to the inside of the sheeting using weld pins and speed clips. Bend over the ends of the pins if necessary to avoid contact with the inner steel sheeting when installed. The inner sheeting may now be fixed to the frame, again as shown in Figure 21. The sound absorbing rockwool or glasswool batts may now be fixed to the inside of the inner sheet using weld pins, speed clips, and a suitable facing (wire, meshing, perforated foil). Alternatively, a perforated metal (such as Bradford ACOUSTICLAD ) or expanded metal can be used, or for an aesthetically pleasing finish. Any gaps, openings or joins in the outer leaf of the enclosure, should be caulked and doors should use acoustic door seals. FIG 22. A PARTIAL ENCLOSURE. Products. Bradford Rockwool FIBERTEX 350, 450. Bradford Glasswool FLEXITEL, SUPERTEL, ULTRATEL. Bradford ULTRAPHON facing. Partial Enclosures & Screens. It is not always practical to totally enclose a noisy machine. However, the use of a partial enclosure or screening will still achieve some reduction in noise levels particularly close to the screens. The previous discussion on total enclosures also applies to partial enclosures. However the overall noise reduction of partial enclosures will not be as great, due to the openings. As far as is practical, employee work stations should be located in the shadow zone of the screening and not in line with the openings in the enclosure. Reflective surfaces near openings in a partial enclosure should be treated with rockwool or glasswool insulation to absorb noise. Where a particular noise source contributes significantly to the overall noise level in a room, it may be controlled by a partial enclosure of the type shown in Figure 22. Much of the sound produced within the enclosure is absorbed, thus reducing the amount of sound radiated into the room. Partial enclosures can be simply fabricated by sandwiching FIBERTEX Rockwool or Glasswool Batts between an outer sheet of plywood and an inner lining of pegboard. Alternatively, plain hardboard, particleboard, plasterboard, or sheet metal may be used for the outer sheet, while the inner lining may be perforated or expanded metal. The effectiveness of a partial enclosure depends in part on the weight of the outer sheet and the percentage of the machinery that is enclosed. FIG 23. TYPICAL NOISE PROBLEM WITHOUT ACOUSTIC ENCLOSURE. FIG 24. IMPROVED NOISE CONTROL WITH A PARTIAL ENCLOSURE. 32

33 The choice of which type of Bradford FIBERTEX Rockwool or Glasswool to use should be based on the frequency spectrum of the noise source. Select the material with the highest sound absorption for the dominant frequency bands of the noise source. High frequency sound absorption will be affected by the inner lining. Should the dominant frequency bands of the noise source be above 1000 Hz, the inner lining should have a perforated open area of 11% or more to ensure optimum sound absorption. The effect of local absorption will be limited by the need to provide access or ventilation to the equipment concerned. However, local absorption permits reduction in sound levels without significantly altering the room reverberation time. Figures 23 and 24 show a typical application of a partial enclosure to reduce noise reaching an operator. Figure 23 and 24 illustrate the use of partial acoustic enclosures in a car assembly line application. Products. Bradford Rockwool FIBERTEX 350, 450. Bradford Glasswool FLEXITEL, SUPERTEL, ULTRATEL. Bradford ULTRAPHON or HD Perf. facings. FIG 25. TYPICAL NOISE PROBLEM WITHOUT ACOUSTIC ENCLOSURE. FIG 26. TYPICAL PARTIAL ACOUSTIC ENCLOSURE APPLICATION. 33

34 ACOUSTIC SCREENS. Simple acoustic screens may be fabricated as shown in Figure 27, and these may be supported in any framing suitable to the particular application. Screens can act in three ways: As local sound absorbers (i.e. a simple partial enclosure), As reverberation control (i.e. more absorption is introduced to the room), As a partial barrier (i.e. an acoustic shadow zone is created behind the screen). For maximum effect, acoustic screens should be located as close as practical to the noise source or to people affected by the noise. They should be as large as possible, at least the height or width of the machine or noise source. Air flow requirements should be considered. Vibration Damping. Vibrating surfaces such as fan casings, pipes, and ducting can be a major source of noise. Lagging these surfaces will significantly reduce the noise radiated from the sources. When treating such surfaces in this manner, it is essential that lagging be applied over the entire sound-radiating surface. It is also necessary to avoid bridging connections between the radiating surface and the outer cladding. Otherwise, the vibration will be transmitted directly to the cladding which will itself become a sound-radiating surface. FIG 28. FIXING STEEL SHEET TO MINIMISE NOISE TRANSMISSION. Products. Bradford Rockwool FIBERTEX 350, 450. Bradford Glasswool SUPERTEL, ULTRATEL. Bradford ULTRAPHON facing. FIG 27. A SIMPLE ACOUSTIC SCREEN. Enclosure Frame Fixing Screw Other steel Sheet Rubber Grommet Fibertex Rockwool or Glasswool Heavyweight plywood or metal core Decorative, non-reflective fabric Protective metal edges VIBRATION ISOLATION. Vibration isolation involves the isolation of vibrating machinery from the building structure. In practice this is achieved by using flexible, resilient mountings, such as rubber-in-shear rubber or steel springs. Where equipment is mounted on inertia blocks, there are often advantages in using a continuous layer of dense rockwool or rubber as the vibration isolator. FIG 29. FIBERTEX ROCKWOOL AS A VIBRATION ISOLATOR. NOTE: Where the noise level emitted by a factory is above acceptable community standards, it is wise to engage the services of a noise control engineer. Environmental noise legislation is quite complex, and failure to comply with the relevant noise criteria may result in severe penalties. Each situation presents its own unique problems which must be identified and then corrected. Resilient Fibertex Rockwool HD Waterproof Film Inertia Block Z-Section Plant Room Floor 34

35 By acting equally under the entire area of the block, the layer of rockwool dampens the rocking motion that may be present and eliminates point loading on the structural floor. The static deflection characteristics of CSR Bradford Insulation products are shown in Product Guides. The use of rockwool as an isolator is not recommended where the required static deflection exceeds 10mm. In such cases it is advisable to use rubber or steel springs. VIBRATION RESISTANCE. Bradford FIBERMESH is particularly suitable for applications involving both vibration isolation as well as high temperature, where standard bonded insulation materials are less resistant to the effects of vibration. Bradford FIBERMESH rockwool is stitched to wire mesh making the blankets especially resistant to fallout under conditions where vibration is present. FIG 30. DENSE GLASSWOOL BOARD USED FOR VIBRATION ISOLATION OF MACHINES. FIG 31. TYPICAL APPLICATIONS OF ARMAFLEX (a) PIPE SUPPORT. FIG 32. TYPICAL APPLICATIONS OF ARMAFLEX (b) PENETRATION THROUGH SOUND INSULATING WALL. Use vibration absorbing flexible couplings on all rigid connections to the vibration source Sound Insulating Wall Pipe False flange (must not contact pipe) Bradford Armaflex Flexible Pipe Insulation Flexible Mastic (sealing gap between flange and pipe) Bradford Quietel Glasswool Board for vibration isolation Isolation of machinery from the floor structure will not achieve its design performance if flanking vibration paths remain. All connections to the equipment, such as piping, ductwork, and electrical conduits, should incorporate a vibration absorbing flexible coupling, and should also be isolated from the building structure by flexible mounts. ARMAFLEX flexible pipe insulation, a closed cell nitrite rubber tubing, provides an excellent vibration isolation gasket for piping and conduit. Typical applications are shown in Figures 31 and 32. INSTALLATION RECOMMENDATIONS. Installation commences with the laying of a suitable waterproof film on the plant room floor. The FIBERTEX Rockwool batts are laid flat on the film, ensuring all joints are tightly butted. The area covered by the batts should exceed the dimensions of the inertia block by at least 50mm on each side. The waterproof film should be wrapped around the outer edges of the FIBERTEX Rockwool batts and retained in position by metal U-channels, timber battens, or other suitable protective treatment. The edging material, when installed, must allow for a 3mm gap between itself and the inertia block. This gap, and any gaps or joins in the edging material should be sealed with a flexible, waterproof mastic. 35

36 Air Conditioning Noise Control. Noise arises in air handling systems principally from fans and from air flow generated noise in both ducts and through registers. It is sometimes necessary to deal with sound transmitted along a duct from one room to another. This section provides methods and data to assist in the design of internal duct lining to control noise. The fan in air conditioning systems is generally the main noise source. The types of fans used are either axial type or centrifugal type fans. Axial fans generate a higher proportion of high frequency noise but less low frequency noise than centrifugal fans of similar duty. The fan manufacturer should be able to supply sound power spectrums of fan noise. Noise also arises from airflow generated in both the ducts and registers (also known as regenerated noise). Usually the greater the velocity of the air through the ducts, the higher the regenerated noise level. NOISE CRITERIA. Noise Criteria curves (NC) and Noise Rating numbers (NR) have been developed to approximate loudness contours and speech interference levels at particular frequencies. These criteria graphs indicate a sound pressure level at each frequency that will be appropriate in a particular environment. Noise Rating numbers are covered by Australian Standard AS1469 : 1983 Acoustics Methods For The Determination Of Noise Rating Numbers. Sound levels are often expressed in A-weighted decibels. Australian Standard AS2107 : 1987 Acoustics Recommended Design Sound Levels And Reverberation Times For Building Interiors covers the recommended background sound levels for occupied spaces makes use of the db(a) weighting. It is recommended that design calculations of noise reduction use Noise Rating numbers and then convert to db(a) at the end of the calculations. GENERAL PROCEDURE. The fan sound power level is first established, then each duct path is examined separately. Noise generated by 90 elbows and branches is estimated using data from the Sound and Vibration section of the ASHRAE Guide and Data Book and added to the fan noise. From this is deducted any branch take-off losses and the natural attenuation due to straight runs of duct work, elbows and end reflections losses, again using the data tabulated in the ASHRAE Guide. The resultant sound power level represents the noise reaching the conditioned space. This is compared to the design requirements for the space based on the selected Noise Rating number plus corrections for the characteristics of the room and the distance to the nearest occupant. If the design goals have not been achieved, the additional attenuation needed at each frequency band must be designed into the system. Duct attenuators can be used, however the most economical approach where space permits is using internal duct liners. FAN NOISE. Generally the fan manufacturer will provide data on fan noise characteristics. However if no data is available, the following empirical formulae developed by Beranek may prove useful: SWL = log kw + 10 log P SWL = log Q + 20 log P SWL = log kw - 10 log Q Where: SWL = overall fan sound power level, db kw = rated motor power, kw P = static pressure developed by fan, mm w.g. Q= volume flow delivered, m 3 /h Octave band sound power levels are then found by subtracting correction factors from the overall sound power level calculated by any one of the above formulae. Maximum noise usually occurs from the blade tip frequency of the fan. This is determined from the number of blades on the fan rotor multiplied by the number of revolutions per second. The octave band in which the blade tip frequency falls will have the highest sound power level and therefore the smallest correction factor to be subtracted from the overall sound power level. A fan s rotating blades produce tones at the blade pass frequency (BPF). rpm x 60 BPF = N Where: BPF = blade pass frequency (Hz) rpm = revolutions per minute N = number of fan blades Harmonics and sub-harmonics may result at frequencies which are multiples of the blade pass frequencies. The recommended correction factors are indicated in Table 9. 36

37 TABLE 9. CORRECTIONS FOR FAN SOUND POWER LEVELS. Blade Tip Frequency 1st 2nd 3rd 4th 5th 6th Fan Type Band Octave Octave Octave Octave Octave Octave Centrifugal Backward Curved Blades Forward Curved Blades Radial Blades Axial Mixed Flow DUCT ATTENUATION. Air handling duct work is internally lined using rockwool or glasswool insulation boards or blankets faced with an acoustically transparent facing to provide adequate sound absorption by the insulation. In addition the facing must provide minimal airflow resistance inside the duct and may also need to act as a vapour barrier. For maximum sound absorption, the duct liner s facing should be as light and porous as possible to allow sound to penetrate it. Internal duct liners commonly use Bradford R-rated Ductliners, SUPERTEL or ULTRATEL Glasswool faced with: Bradford ACOUSTITUFF Bradford ULTRAPHON woven glass fabric, Lightweight THERMOTUFF, Heavy Duty 750P THERMOFOIL perforated, Black or clear fibreglass tissue or Fine, lightweight polyester films (Mylar or Melinex). Appendix C, Table C7, Contains comparative noise reduction coefficients for Bradford products. The most important octave bands where fan noise is concerned are the 125Hz and 250Hz bands. Ducts internally lined with a suitable length and at least 50mm thickness of Bradford Glasswool or FIBERTEX Ductliner can effectively reduce the low frequency component of fan noise. The thicker the internal duct liner, the better the low frequency sound absorption. The thermal performance of the insulation for air conditioning ducts can be calculated using the data in the CSR Bradford Insulation Air Conditioning Design Guide. Table 10 is a guide to the attenuation achieved by lining two opposite sides of a duct with Bradford Glasswool ULTRATEL at 50mm and 100mm thickness. The distance D is the depth in mm between the linings. It is assumed that any facing material used is deemed acoustically transparent. If the duct is to be lined on all four sides, the total attenuation may be obtained by arithmetically adding the attenuation achieved by lining the other two opposite sides. TABLE 10. CALCULATED LINED DUCT ATTENUATION, db/m. Lining Depth Between Linings D Frequency (Hz) Thickness mm mm mm Limit of Attenuation Table 10, shows that the smaller the duct dimensions, the higher the attenuation per length of duct. 1 Sound Research Laboratories, Noise Control in Building Services, Pergamon Press, First Edition

38 Straight Duct Circular/Oval or Rigid Walled (unlined) Straight Duct Rectangular (unlined) x ACOUSTIC DESIGN GUIDE x x TABLE 11. ATTENUATION OF UNLINED DUCTS. Duct Dimensions x (mm) Duct Dimensions x (mm) Octave Band Centre Frequency Hz) k 2k 4k Attenuation db/metre run Octave Band Centre Frequency Hz) k 2k 4k Attenuation db/metre run TABLE 12. IN-DUCT ATTENUATION WITHIN EXTERNALLY LAGGED DUCTS. Straight Duct Duct Dimensions Circular/Oval or (externally lagged) x (mm) x Straight Duct Rectangular (externally lagged) x x Duct Dimensions x (mm) Octave Band Centre Frequency Hz) k 2k 4k Attenuation db/metre run Octave Band Centre Frequency Hz) k 2k 4k Attenuation db/metre run Straight Duct Circular/Oval or Rigid Walled (unlined) D D TABLE 13. ATTENUATION OF RADIUS BENDS. Duct Dimensions D (mm) Octave Band Centre Frequency Hz) k 2k 4k Attenuation db For more examples of duct losses, refer to ASHRAE (American Society Of Heating Refrigeration Engineers) publications. It should be noted, that a limit to the attenuation of sound in duct work may be imposed by flanking transmission or noise breakout. This particularly occurs when the aim is to achieve high attenuation in a short length of straight duct. There are positive steps that can be taken to counter the effect of flanking transmission but for the purpose of this guide it is recommended that, in using these Tables, reliance should not be placed on achieving attenuation in excess of the limiting values shown. If attenuation beyond these limits is required, it should be achieved by other acoustic treatment or lining at a location remote from the length of duct under consideration. 38

39 TABLE 14. ATTENUATION OF MITRE (90 ) BENDS. Mitre Bend (unlined) D Duct Dimension D (mm) Octave Band Centre Frequency Hz) k 2k 4k Attenuation db Mitre Bend (lined) D Lining Thickness = 10 Lining to extend distance 2D or greater D Duct Dimension D (mm) Octave Band Centre Frequency Hz) k 2k 4k Attenuation db

40 MEASURED SOUND ATTENUATION IN DUCTS. CSR Bradford Insulation has carried out extensive research to establish the real performance of duct liners in reducing noise levels. Tests have been carried out on Bradford Insulation 25mm and 50mm duct liners using different duct sizes and lengths of lined duct. Figures 33, 34 and 35 have been plotted from measurements of sound levels taken in standard sheetmetal ducts using 25mm duct liners. The graphs present a conservative guide to the performance of all Bradford Glasswool and Fibertex Rockwool duct liners at 25mm thickness. Four different lengths of lining are shown for each of three duct sizes. FIG 34. SOUND ATTENUATION IN DUCT SIZE 406 x 813mm. Insertion Loss (db) Frequency (Hz) Bend 4.9m 3.7m 2.4m 1.2m FIG 33. SOUND ATTENUATION IN DUCT SIZE 254 x 305mm. 60 FIG 35. SOUND ATTENUATION IN DUCT SIZE 508 x 610mm Insertion Loss (db) m 3.7m 2.4m Insertion Loss (db) Bend 10 Bend 1.2m m 3.7m 2.4m 1.2m Frequency (Hz) Frequency (Hz) TABLE 15. INSERTION LOSS CHARACTERISTICS OF FACED DUCTLINERS. (INTERNAL DUCT LINING) Insertion Loss (db loss 600x600x4000 test duct) Product Facing Thickness Octave Band Centre Frequency (Hz) mm Bradford Glasswool BMF DUCTLINER THERMOFOIL 32 kg/m 3 HD Perf µm Melinex + THERMOFOIL HD Perf. ACOUSTITUFF ULTRAPHON Bradford Premium Ductliner ULTRATEL ACOUSTITUFF kg/m 3 Bradford FIBERTEX THERMOFOIL DUCTLINER HD Perf kg/m 3 40

41 Research has also been carried out on sound attenuation characteristics of different facing materials used on duct liners. Insertion Loss measurements carried out in accordance with Australian Standard AS1277 : 1983 Acoustics - Measurement Procedure For Ducted Silences demonstrate the effect of typical facing materials on the acoustic performance of Bradford Glasswool and FIBERTEX duct liners, as shown in Table 15. An alternative rough indication of attenuation achieved by the lining of ductwork can be found by use of the Sabine formula. This gives reasonable results for straight ducts at low frequencies provided the smallest duct dimension is within the range 150 mm to 450 mm and the width is no greater than three times the depth Pα Attenuation (db/m) = 1.4 A Constraints accuracy = ± 10% frequency range, 250 to 2000Hz α 0.8 for circular ducts, Diameter > 0.15m for rectangular ducts, width or height 900mm and width 0.5 < < 2 height The location of duct lining can be a critical factor. It is normally placed at the start of a duct system to attenuate fan noise and near the outlets to correct air flow generated noise from dampers and fittings, and to restrict noise transmission from adjacent areas through the air conditioning duct. Where: P = inside perimeter of lined duct, m A = internal cross-sectional area, m 2 α = absorption coefficient of the duct liner at the frequency concerned. D a b TABLE 16. SOUND ABSORPTION OF BULK INSULATION DUCTLINERS. Product Facings Thickness Frequency (Hz) (mm) NRC* Bradford Glasswool THERMOFOIL DUCTLINER/ HD Perf SUPERTEL BMF kg/m ULTRAPHON ACOUSTITUFF Bradford Glasswool THERMOFOIL Premium HD Perf DUCTLINER/ ACOUSTITUFF ULTRATEL 48kg/m Bradford THERMOFOIL FIBERTEX HD Perf DUCTLINER BMF kg/m Bradford FIBERTEX 450 ULTRAPHON kg/m 3 ACOUSTITUFF * NRC: Arithmetic average of absorption coefficients of frequency 250, 500, 1000 and 2000Hz. 41

42 ATTENUATION OF LINED BENDS. The application of acoustic lining to bends can be very effective in attenuating duct-borne sound. Square elbows are preferred to radius bends. The lining should have a thickness at least 10% of D, the clear width between the two linings (refer diagram), and the length of lining should extend a distance not less than 2D before and after the bend. Table 17 gives attenuation in db achieved by square elbows without turning vanes when lined as recommended. FIG 37. SOUND ATTENUATION IN LINED PLENUM. θ d FIG 36. SOUND ATTENUATION BY LINED SQUARE ELBOWS. Lining Thickness (10% of D min.) Acoustic Lining TABLE 17. ATTENUATION BY LINED SQUARE ELBOWS, db. D Frequency (Hz) (mm) ATTENUATION BY LINED PLENUMS. The acoustical lining of fan discharge and suction plenums is often the most economical and convenient approach to achieving a major part of the sound attenuation required in a system. The following formula gives an approximate value of the attenuation achieved by this means (refer diagram). (cosθ) 1 α Attenuation = 10 log 10 [S o + S o ] (2πd 2 ) αs w Where: α = absorption coefficient of the lining S o = area of outlet opening, m 2 S w = total plenum wall area, m 2 d = slant distance, centre inlet to centre outlet, m θ = angle of incidence at the outlet, degrees. 2D D AIR FRICTION. The energy absorbed by frictional losses in the air handling system may be significant, particularly for high velocity systems. The following information will assist the designer in assessing the effect of duct liners upon frictional losses. The usual procedure for determining friction losses in air ducts is by use of the Air Friction Charts published by the ASHRAE Handbook of Fundamentals and the IHVE Guide. These charts provide friction losses for sheet metal ducts of standard construction. These losses must be multiplied by a factor to correct for the influence of duct liners. The following graph shows correction factors for the Bradford range of Glasswool and FIBERTEX Rockwool duct liners. It is based on actual tests on a lined duct of 460 x 200mm internal dimensions, equivalent to a 280mm diameter circular duct. To adjust the correction factor selected for ducts of other dimensions, increase by up to 10% for circular equivalent sizes down to 150mm and decrease by up to 10% for circular equivalent sizes up to 1000mm. FIG 38. AIR FRICTION CORRECTION FACTOR. Correction Factor Air Velocity (m/s) 1 = Black Matt tissue (BMF) Faced Ductliners. 2 = THERMOFOIL Perforated Foil Laminate Faced Ductliners

43 RESISTANCE TO AIR EROSION AND RECOMMENDED VELOCITIES Bradford Glasswool and FIBERTEX Rockwool ductliners have been tested for surface erosion at extreme velocities by the quantitative method developed by the CSR Building Materials Research Laboratories, based on Underwriters Laboratory Standard UL The products were subject to velocities up to 40m/s and then a safety factor of 0.4 applied in accordance with the Underwriters Laboratory test. On the basis of these results and typical air friction correction factors from ASHRAE, the following maximum design velocities are recommended. TABLE 18. MAXIMUM DESIGN VELOCITY. Product Maximum Design Velocity (m/s) Bradford Glasswool Covered with Perforated Metal 23 Faced with Perforated Foil 18 Faced with Black Matt Tissue (BMF) 22 Faced with ACOUSTITUFF 30 Faced with ULTRAPHON 26 Bradford FIBERTEX Rockwool FIBERTEX Ductliner CF covered with Perforated Metal 23 FIBERTEX Ductliner with Perforated Foil18 FIBERTEX Ductliner faced with Black Matt Tissue (BMF) 22 EXTERNAL DUCT LAGGING. External lining (lagging) of air conditioning ducts with foil faced rockwool or glasswool reduces duct breakout noise by damping the duct. Some of the noise which breaks out through the lagged duct is absorbed by the surrounding insulation. The sound attenuation achieved inside the duct is also enhanced by duct lagging particularly at low frequencies, up to about 500Hz. Air handling ducts are commonly lagged using: Bradford FIBERTEX Rockwool Ductwrap Bradford Glasswool MULTITEL or FLEXITEL with Medium or Heavy Duty THERMOFOIL. Bradford Glasswool THERMOGOLD Ductwrap. DUCT BREAK OUT-NOISE. Noise breakout from ducts can occur from: Fan noise passing through the duct Aerodynamic noise (also know as re-generated noise), from obstructions fittings etc in the duct Turbulent airflow causing duct walls to vibrate and rumble radiating low frequency airborne noise. Solutions to reduce noise breakout from ducts: Stiffer ducts (circular ducts are better than square or rectangular). External bracing of ducts increases stiffness, however it can improve the radiation efficiency of the duct cancelling the benefit of increased stiffness. Using heavier material for duct walls and increasing damping (ie. thicker steel sheeting). Adding damping (spray on or self adhesive compounds). Acoustic lagging, preferably with a heavy limp impervious layer isolated or decoupled from the duct with either glasswool (such as Bradford ACOUSTILAG ) or rockwool. The solutions to reduce noise breaking out from ducts can be expensive. Therefore it is more cost effective to avoid noise break out problems than to try to correct them later. DUCT BREAK-IN NOISE. Noise inside ceiling plenums or from air conditioning equipment, plant rooms etc, can break into ducts, particularly flexible ducts and then be carried into rooms or spaces below. Flexible ducts, due to their light weight, flexibility, speed and ease of installation, are commonly used in air conditioning systems. Noise can more easily penetrate flexible ducts because of their lightweight nature. To avoid break-in noise, the following can be used: Where possible, avoid ducts passing through noisy areas as this can significantly increase noise through the air conditioning system. Replace lightweight flexible ducts with heavier ducting such as sheet steel. The flexible ducts can be enclosed in a solid enclosure constructed from timber, plasterboard or sheet steel, etc. Before enclosing flexible ducts, it should be noted that noise in the ceiling cavity will most likely penetrate the ceiling. This will happen more so if lightweight lay-in tiles using metal grids are used. Fixed plasterboard ceilings give better acoustic performance than lightweight ceiling tiles. 43

44 FLOW GENERATED NOISE. Turbulent noise in ducts is generated from the following: Objects such as dampers, grilles, rods, etc. Constrictions in duct cross sectional area, orifice plates, silencer splitters etc. Jet noise, inlet or discharge noise flowing through orifices. Boundary layer turbulence, air passing over the inner surface of the duct. Flow around bends and duct take offs (branches). These sources cause turbulence in ducts and this noise is also known as re-generated noise. The intensity of the re-generated noise depends upon the velocity of the air in the duct. FIG 39. LOCATION OR DUCT ATTENUATOR. Plant Room Bad location Noise break-out from noisy side of attenuator END REFLECTIONS. At the end of a duct (register, diffuser grille etc.) the air meets a large increase in volume. This allows expansion of the air providing useful sound energy losses at the low frequencies. This is termed end reflection loss. A higher number of small registers spaced well apart will transmit less low frequency noise into a room than one large single register. Plant Room Bad location Noise break-in to quiet side of attenuator DUCT ATTENUATORS OR DUCT SILENCERS. Duct attenuators or silencers are used where high attenuation is required. These silencers usually consist of sheet steel duct housing containing sound absorbent splitters usually made of rockwool or glasswool. The silencer s attenuation is normally quoted as an insertion loss in octave frequency bands. Silencers cause a pressure drop across them and also regenerated noise through the splitters, which increases with the air velocity through the ducts. Silencers should ideally be located where the duct leaves the plant room (see Figure 39). Care must be taken to avoid plant room noise from entering the quiet side of the silencer. Standard silencers incorporate a perforated metal screen backed by Bradford Glasswool or Bradford FIBERTEX Rockwool faced with black fibreglass tissue (BMT). An alternative design, particularly for smaller systems, is to face the rigid insulation with Bradford ULTRAPHON wrapped or taped around the edges and glued into the C-channel supporting the frame. Test results are shown in Appendix C, Table C9. Bradford FIBERTEX Rockwool is recommended for high temperature attenuation such as hot gas exhausts. Plant Room Ideal (but impractical ) location Plant Room Good practical location 44

45 FLANKING THROUGH AIR CONDITIONING DUCTS. Where two rooms are served by common ducts, sound (ie speech, machinery noise etc) can travel from one room and into the next room via the duct. In some buildings, speech can be heard through ducts. This is also known as crosstalk. Crosstalk or sound through ducts can be attenuated by: internally lining ducts with rockwool or glasswool. increase the length of internally lined duct between offices. (Refer to Figure 40). increase the amount of end reflection (more smaller registers are preferable to fewer larger registers). fitting duct silencers. modifications to room layouts to reduce crosstalk. Products Internal Duct Lining: The following glasswool blankets are generally used for internal duct lining: Bradford SUPERTEL Glasswool (32kg/m 3 ). Bradford R-rated Ductliner (32kg/m 3 ). Bradford FIBERTEX Rockwool Ductliner (60kg/m 3 ). The above Glasswool blankets can be faced with: ULTRAPHON (black glass cloth fabric) ACOUSTITUFF (lightweight foil facing) Heavy Duty THERMOFOIL 750P perforated, (optional: Mylar film between blanket and foil to prevent fibre release). Fine, lightweight polyester films (Mylar or Melinex). Black or clear fibreglass tissue. Products External Duct Lagging: Bradford THERMOGOLD Ductwrap (18kg/m 3 ). Bradford MULTITEL Glasswool (18kg/m 3 ) with Medium Duty THERMOFOIL. Bradford FLEXITEL Glasswool (24kg/m 3 ) with Medium Duty THERMOFOIL. Bradford FIBERTEX Rockwool Ductwrap (50kg/m 3 ) with Medium Duty THERMOFOIL. Bradford ACOUSTILAG 20 or 23. FIG 40. DUCTWORK LAYOUT TO REDUCE CROSSTALK. Layout To Be Avoided Air Flow Crosstalk Crosstalk path Crosstalk path Crosstalk path Crosstalk path Preferred Layout Air Flow 45

46 Bradford Acoustic Solutions for Specialty Applications. Home Cinema. The current trend in households today is the use of timber floors or tiled floors which are hard and acoustically reflective. These together with reflective walls and ceilings result in long reverberation times not suited to home cinema systems. Under these circumstances, home cinema systems will require more sound absorption in the room to lower the reverberation time closer to the optimum level suited to amplified music and speech. Note that too much absorption will make the room dead and result in poorer quality sound. To lower the reverberation time of a room, install: Decorative fabric faced rockwool or glasswool absorbers on the walls. Velour coated high density rockwool or glasswool on the walls. Perforated timber, Gyprock plasterboard or perforated metal pan ceiling with rockwool or glasswool insulation above. Rugs, carpet, curtains and soft furniture in the room. The acoustic reproduction of many modern home cinema systems is very good, and they can generate high levels of bass sound which penetrates building materials more easily. Low frequency sound is also more difficult to absorb. Therefore the home cinema system room may be a source of noise for others in the household or neighbours, particularly if the volume is loud. These rooms should be treated or sound proofed if they are likely to cause disturbance to others. The following treatments should be considered: Brick veneer walls should use mutli-layers of CSR Gyprock Fyrchek or Soundchek plasterboard to add mass and increase the STC of the walls. Ideally, the wall should have two separate studs with Bradford Rockwool or Glasswool Partition Batts inside the cavity walls. Bradford batts inside cavity partitions can increase the walls acoustic rating by STC 10. If this is not possible then staggered studs or the widest stud cavity available should be used and filled with Bradford Rockwool or Glasswool Partition Batts. Ceilings should include increased mass to increase their STC rating. Multi layers of CSR Gyprock plasterboard can be used with Bradford Rockwool or Glasswool Ceiling Batts above. Floors should be insulated with Bradford Floor Batts particularly if the cinema room is upstairs. (see Floor/Ceiling Noise Control Systems, Appendix B). Windows should be double glazed with preferably different size laminated glass panes to provide better damping. Large air gaps between the glass panes, and properly sealed around the perimeter of the frame also increases the window s acoustic rating. Laminated single pane glass is the next best choice. Doors should be solid core timber or metal with good quality door seals. Preferably double doors or an insulated sound lock should be used. Note that if the room has ducted air conditioning, then flanking can occur through the ducting and sound can pass into the next room. Bradford Products for Walls: Bradford Rockwool or Glasswool Partition Batts. Bradford SoundScreen. Ceilings: Bradford Rockwool or Glasswool Ceiling Batts. Bradford Glasswool Ceiling Panel Overlays. Bradford Rockwool FIBERTEX 350, 450. Bradford Glasswool FLEXITEL, SUPERTEL, ULTRATEL. Bradford Glasswool Absorption Blanket. 46

47 Auditoriums. Auditoriums are a specialised area of room acoustics with many books written on the subject. The acoustic design of auditoriums should be undertaken by an experienced acoustic consultant. This is a simplified guide to the acoustic requirements of auditoriums. The shape and size of an auditorium can have a great influence of the acoustics of the space. It is also very important to control the auditorium s reverberation time so the users can experience good acoustics. General purpose auditoriums can have multiple uses such as speech and amplified music which have conflicting reverberation times. The acoustic designer needs to determine the auditorium s optimum reverberation time for its intended use. Computer software is available that allows modelling the optimum reverberation time for the room. Sound absorbing materials are added to the rooms surfaces to fine tune and optimise the room s reverberation time. Artificial reverberation can be added either acoustically or electronically to modify the sound. The relationship between reverberation time and sound absorption is given by the Eyring s equation (refer to Reverberation Control, page 63). There are a number of methods used to absorb sound in an auditorium. These include: Sound absorbing panels consisting of fabric faced Bradford Rockwool or Glasswool. The decorative facing chosen should be acoustically transparent (with low flow resistance) to maximise sound absorption within the insulation. Decorative open weave fabrics are suitable for these acoustic applications. Bradford ACOUSTICLAD is ideal broad band industrial grade absorber which can be used in auditoriums. Bradford Rockwool or Glasswool behind spaced timber panels (slotted or slatted). The sound travels through the gaps in the timber and is absorbed by the insulation. Alternative treatments include fixing the sound absorbing batts behind perforated panels, such as plywood, Gyprock plasterboard or metal. The use of a BMF (Black Matt Facing) tissue or Bradford ULTRAPHON on the insulation is recommended for aesthetic reasons. Membrane or panel absorbers typically solid, reflective panels (timber, plasterboard etc.) fixed to walls on studwork. Panel absorbers can be tuned to resonate (absorb) sound within a narrow frequency range. Adding rockwool or glasswool insulation in the air cavity of panel absorbers, increase their absorptive frequency range. FIG 41. TYPICAL ACOUSTIC TREATMENTS FOR AUDITORIUM WALLS AND CEILINGS. Acoustic Absorbing Panels on walls Bradford Partition Batts Bradford Acousticon Roofing Blanket Bradford Ceiling Batts 47

48 Cavity absorbers are usually an enclosed volume of air with a small neck/opening (often known as Helmholtz resonators. Cavity absorbers provide a very narrow band of sound absorption, which can be expanded with the use of rockwool or glasswool in the air space. These absorbers have specialised acoustic applications such as studios and auditoria, and for pure tone absorption. Perforated metal ceiling panels with rockwool or glasswool insulation above. The size, number of perforations, insulation type, thickness and density can affect the frequency at which maximum absorption occurs. On occasions, auditoriums have dual uses, for example speech and amplified music. It is possible to introduce absorption into these auditoriums to lower the reverberation time to suit the acoustic requirements. Temporary absorbing panels can be introduced in the form of sliding acoustic doors, or portable architecturally designed sound absorptive structures to suit the decor of the auditorium. Sound absorption is often required on the rear wall of the auditorium to stop unwanted reflection of sound. The personal address system amplifier, type and size of microphones, number of speakers, sound delay, etc., also need to be considered. It is important to stop unwanted noise from entering the auditorium from people, air conditioning, road and rail traffic, aircraft, public amenities, foyers, rain etc. To reduce extraneous noise from entering the auditorium: Fill any wall cavities with Bradford Rockwool or Glasswool Partition Batts. Install Bradford ACOUSTICON foil faced roofing blanket under steel roofing to reduce rain noise by up to 18dB(A). Refer to Rain Noise Reduction with Metal Deck Roofing, page 20. Internally line air conditioning ducts with rockwool or glasswool (either using foil facing, fine fibreglass tissue, Bradford ACOUSTITUFF or ULTRAPHON. Externally lag ducts with rockwool or glasswool faced with Bradford Thermofoil facing. Consider the use of duct silencers to reduce air conditioning noise levels. Locate the plant room of the air conditioning system away from the auditorium. If this is not possible, then acoustically treat the plant room with high STC walls, roof/ceiling, floors, doors etc. Lag waste pipes inside auditorium with Bradford Acoustilag 23 or 26. Install acoustic door seals on door perimeters or absorbent sound locks. Products. Bradford Glasswool or Rockwool Partition Batts. Bradford FIBERTEX Rockwool. Bradford Glasswool MULTITEL, FLEXITEL, SUPERTEL or ULTRATEL. Bradford FIBERTEX Rockwool Ductliner (60kg/m 3 ). Bradford ACOUSTICLAD. Bradford Rockwool or Glasswool Ceiling Batts. Bradford Glasswool ACOUSTICON. Bradford Rockwool or Glasswool Ductliner. Bradford ACOUSTILAG 23 or 26. Insulation facings: Bradford THERMOFOIL (Light, Medium and Heavy Duty or Heavy Duty perforated). Bradford THERMOTUFF foil. Bradford ULTRAPHON. Bradford ACOUSTITUFF. Black or clear fibreglass tissue. Sports Complexes. Sporting complexes can suffer from poor acoustics due to the high reverberation times caused by the lack of sound absorptive finishes within the space. This can result in difficulty understanding speech. Sporting complexes therefore, require sound absorptive material to be added to achieve a lower reverberation time suitable for speech. (Refer to Table A5, page 64). The following describes ways to add sound absorption in a sporting complex: Fabric faced rockwool or glasswool acoustic absorbers for the walls. Velour coated high density rockwool or glasswool absorbers for the walls. Bradford ACOUSTICLAD wall/ceiling absorber. Porous absorbers such as rockwool or glasswool insulation with a perforated facing of; metal, timber, or Gyprock plasterboard etc. The use of a fine fibreglass tissue facing BMF (Black Matt Facing) tissue or Bradford ULTRAPHON on the insulation can be used for aesthetic reasons and eliminates fibre release. Bradford ACOUSTICLAD wall and ceiling absorber is durable and its high acoustic absorption is an excellent choice for sports complexes. ACOUSTICLAD offers excellent test results with NRC ranges from 0.9 to

49 FIG 42. TYPICAL ACOUSTIC TREATMENTS FOR SPORTS COMPLEX. Bradford Acousticon Roofing Blanket Bradford Acoustic Baffles Bradford Partition Batts Acoustic Absorbing Panels Bradford Wall Batts Bradford Rockwool or Glasswool behind spaced timber panels (slotted or slatted). The sound enters the insulation through the gaps in the timber and is absorbed by the insulation. To reduce rain nose under metal roofing, install Bradford ACOUSTICON foil faced roofing blanket under the metal deck. This can reduce rain noise by up to 18dB(A) and improve the STC rating of the roof. To reduce timber floor impact noise, use a resilient materials such as rubber, dense rockwool or glasswool, rubber/cork compounds etc., beneath the battens or floor joists and the floor supports. For existing floors, a floating floor can be constructed above the existing floor with a resilient material layer between the two flooring systems. The correct stiffness of the damping layer should be selected for both the static and dynamic loads. The two floors should not be mechanically fixed with nails or screws as this would make the damping material redundant. It is advisable to consult an acoustic consultant for vibration isolated flooring systems. If the sports complex is on a second storey of a building, install Bradford Rockwool or Glasswool Ceiling Batts beneath the complex s floor in the floor/ceiling cavity. Bradford Products. Bradford ACOUSTICLAD wall/ceiling absorber. Bradford FIBERTEX ROCKWOOL. Bradford Glasswool FLEXITEL, SUPERTEL or ULTRATEL with optional BMF, ULTRAPHON or THERMOFOIL facings. Bradford ACOUSTICLAD. Bradford Glasswool ACOUSTICON. Bradford Rockwool or Glasswool Ceiling Batts. 49

50 Canteens/Restaurants. Canteens and restaurants that have hard floors, walls and ceilings, are very reverberant, especially when full of diners and music. Noise is generated from voices and cutlery. Often soft music is used to provide an ambience and some acoustic masking. These noise sources make communication difficult, and people tend to raise their voices to be heard, which in-turn increases the noise level in the room. Canteens and restaurants can benefit from added sound absorption in the room to control reverberation. To lower the reverberation time within a canteen or restaurant, install: Fabric faced rockwool or glasswool absorbers on the walls. Bradford ACOUSTICLAD perforated metal wall absorber with rockwool or glasswool insulation (encapsulated in a thin polyester film such as Mylar or Melinex to stop fibre release). Perforated timber, Gyprock plasterboard or perforated metal pan ceiling with rockwool or glasswool insulation above. Insulation should be encapsulated to stop fibre release. Note that too much absorption may make the room acoustically dead, and can result in a lack of acoustic privacy for diners. If the canteen or restaurant has a noise sensitive area above, below or adjacent to it, the facades should have higher acoustic performance (STC ratings) to stop noise breaking-out, ie. multi-layers of heavier Gyprock Fyrchek on walls and ceilings, with Bradford Rockwool or Glasswool Partition/Ceiling Batts installed. Heavier glazing and addressing flanking paths should also be considered. (Refer to additional information detailed for Walls, Roof/Ceilings and Floors). Products. Bradford FIBERTEX Rockwool. Bradford Glasswool or Rockwool Partition Batts. Bradford Glasswool FLEXITEL SUPERTEL or ULTRATEL with BMF or ULTRAPHON. Bradford ACOUSTICLAD. Bradford ACOUSTICON. Karaoke & Nightclubs. Karaoke Rooms and Nightclubs will require reverberation times optimised for music. Amplified music played in these venues has considerable low frequency bass energy. To optimise the acoustics, the reverberation times should be slightly longer at the lower frequencies. To control reverberation in these rooms use: Porous absorbers Fabric faced rockwool or glasswool absorbers for the walls. Perforated timber, Gyprock plasterboard or perforated metal pan ceiling with rockwool or glasswool insulation above. Bradford ACOUSTICLAD perforated metal panel ceiling system. Membrane or panel absorbers. FIG 43. TYPICAL ACOUSTIC TREATMENTS FOR CANTEEN/RESTAURANT APPLICATIONS. FIG 44. TYPICAL ACOUSTIC TREATMENTS FOR KARAOKE ROOM/NIGHTCLUB APPLICATIONS. Bradford Insulation in partition walls Bradford Acoustic Wall Absorbers Bradford Insulation in partition walls Bradford Acoustic Wall Absorbers Bradford Acousticon under metal deck roof Bradford Insulation above perforated ceiling system Bradford Insulation above perforated ceiling system 50

51 Karaoke rooms and nightclubs can cause disturbance for others nearby as music sound levels inside can reach or exceed 100dB(A). These rooms should be sound proofed if they are likely to cause disturbance to others. To do this, building envelopes with very high STC ratings are required. The following acoustic treatments are recommended. WALLS. Use multiple layers of CSR Gyprock Fyrchek plasterboard to add mass and increase the STC of the walls. (The more mass that is used, the higher the STC rating). Ideally, the wall should have two separate studs with Bradford Rockwool or Glasswool Partition Batts inside the cavity of the walls for an increase of up to 10 STC. If this is not possible, then staggered studs or the widest possible stud cavity should be used (to reduce low frequency sound transmission) and filled with Bradford Rockwool or Glasswool Partition Batts. CEILING. Ceiling should have extra mass added to increase the STC. Multi layers of CSR Gyprock plasterboard can be used with Bradford Rockwool or Glasswool Ceiling Batts above. Beneath the plasterboard ceiling, a suspended perforated metal pan ceiling can be used to provide sound absorption in the room. WINDOWS. Windows should be double glazed with preferably different size laminated glass panes (laminated glass has better damping). Air gaps between the glass panes should be properly sealed around the perimeter. Thicker laminated single pane glass is the next best choice. DOORS. Doors should be solid core timber or metal with good quality acoustic door seals. An insulated sound lock using acoustically treated doors will provide better acoustic performance. Note that for higher STC walls, ceilings and floors, flanking must be considered. (Refer to Flanking Paths, page 59). Some Karaoke restaurants/clubs have many Karaoke booths which require acoustic isolation from each other. It is recommended that high STC rating walls are used to acoustically isolate these rooms from each other. Refer to the CSR Gyprock Fire & Acoustic Design Guide, NºGYP500 to choose a wall system. Flanking paths should also be considered when acoustically isolating rooms requiring high STC ratings. Sometimes these flanking paths can be the limiting factor in obtaining acoustic privacy from room to room. It is advisable to engage the services of an acoustic consultant to design sound proofing for rooms with very high noise levels, in particular, Karaoke rooms and nightclubs. Products. Bradford Rockwool FIBERTEX 350, 450. Bradford Glasswool FLEXITEL, SUPERTEL, ULTRATEL. Bradford Glasswool Absorption Blanket. Bradford Glasswool Ceiling Panel Overlays. Bradford Rockwool or Glasswool Partition Batts. Bradford ACOUSTICLAD. Shopping Centres. In shopping centres, the designers should look at noise control in the following areas: Between shops to provide acoustic privacy refer to sections in this book on wall and ceiling insulation. Reverberation control within the shopping centre open areas (ie. stage and dining areas). Rain noise under steel roofing install Bradford Acousticon hard under steel deck roofing. Air conditioning and mechanical services noise acoustically treat plant room, internally line and externally lag air conditioning and air extraction ducts, particularly where they are exposed. Plant rooms should use high STC rating walls, ceilings and floors if next to noise sensitive areas. Plant room walls should be lined with Bradford Acousticlad to absorb noise. Carpark noise avoid steel speed humps which work lose with time and become noisy. Products. Bradford Rockwool or Glasswool Partition Batts. Bradford FIBERTEX Rockwool. Bradford Glasswool SUPERTEL, ULTRATEL. Bradford ACOUSTICON. Bradford ACOUSTICLAD. 51

52 Music Rooms, Recording Studios, Radio & Television Rooms. The optimum reverberation time required in a music studio depends on the size of the room. Music recording studios and radio or television broadcasting rooms require very short reverberation times or a dead acoustic environment. To achieve shorter reverberation times with smaller room volumes, more sound absorption is required. The reverberation times for the room should be set for each octave or more accurately each 1 / 3 octave band. Generally for music, the lower frequencies require higher reverberation times. For speech the reverberation time should be approximately equal across frequency bands. The relationship between reverberation time and sound absorption is given by the Eyring s equation (refer to Reverberation Control page 63). Sound absorbers do not absorb sound equally in each frequency band. Therefore it is common practice to use a combination of different types of absorbers. There are various types of sound absorbers, including: Porous type absorbers eg. Acousticlad, fabric faced absorbers, perforated metal pan ceilings and moulded foam etc. Panel absorbers (Refer to Room Acoustics, page 64). Cavity absorbers (Helmholtz resonators). The above types add sound absorption inside the room, and are required, to tune the reverberation time as close to optimum for music or recording purposes. It is imperative that extraneous noise does enter into recording studios, radio or television broadcasting rooms. Therefore it is imperative that these rooms are properly sealed or sound proofed. Very high STC walls, doors, windows, roof/ceilings are required. Walls should use mutli-layers of CSR Gyprock Fyrchek with preferably two separate studs to support the walls. Bradford Rockwool or Glasswool Partition Batts should fill the cavity of the walls for an increase of up to 10 STC. Reverberation Time (sec) FIG 45. OPTIMUM REVERBERATION TIMES FOR MUSIC/TV/RADIO STUDIOS Music Studio Room Volume (m3) TV/Talk Studio If steel roofing is used for these rooms, insulate the roof with Bradford ACOUSTICON to reduce rain noise transmission. Ceilings should also use multi layers of CSR Gyprock Fyrchek resiliently mounted to the furring channels. Windows should be double glazed with preferably: Different size laminated glass panes (laminated glass has better damping). Large air gap between the glass. Properly sealed around the perimeter of the frame. Doors should be solid core timber or metal with good quality door seals. Preferably double doors or an insulated sound lock should be used. Recording studios, radio and television broadcasting rooms should also be vibration isolated from the main building structure. This will reduce the transfer of low frequency noise into the space which can affect the acoustics of these rooms. Roads, railway lines, industry etc, can be sources of low frequency noise and vibration. It is advisable to engage the services of an acoustic consultant to design sound proofing for TV/Radio/Music Studios. TABLE 19. RECOMMENDED MAXIMUM BACKGROUND SOUND PRESSURE LEVEL FOR STUDIO APPLICATIONS. Studio Use Octave Band Sound Pressure Level (Hz) Recommended Maximum Background Sound Levels [db] Drama and Music Studios Television and Talk Studios

53 FIG 46. TYPICAL ACOUSTIC TREATMENTS FOR TV/RADIO/MUSIC STUDIO APPLICATIONS. Bradford Insulation in high STC partition walls Bradford Acoustic Absorbers to control reverberation Bradford Insulation treatment to air conditioning ducts Products. Bradford Glasswool FLEXITEL, SUPERTEL, ULTRATEL. Bradford FIBERTEX Rockwool. Bradford ACOUSTICLAD. Heavy Plant. Engine compartments of plant and machinery should be lined with Bradford Rockwool or Glasswool faced with Bradford Heavy Duty 750P THERMOFOIL Perforated to absorb engine and ancillary noise. As engine noise has most energy at low frequencies, insulation thickness should be at least 75mm. The thicker the insulation, the better the low frequency sound absorption. Lightweight sheet steel casings can often vibrate and emit noise. To damp these casings, Bradford ACOUSTILAG can be used. The glasswool side of the Acoustilag should be secured firmly to the outside of the sheet steel to increase the panel s mass. The mass of the loaded vinyl, damps the vibrating panel, and reduces noise. Operators cabins should also be fully enclosed and well sealed to stop noise from entering. Dust inside an operator cabin is a good indication the cabin is poorly sealed. Cabins should also be vibration isolated for operator comfort and safety, and also to minimise re-radiated noise from lightweight materials. The cabin can be lined with rockwool or glasswool insulation with a suitable facing such as perforated THERMOFOIL to absorb noise within the cabin. Products. Bradford FIBERTEX Rockwool. Bradford Glasswool SUPERTEL or ULTRATEL. Bradford ACOUSTILAG. Heavy duty perforated THERMOFOIL. OEM. CSR Bradford Insulation supplies the full range of glasswool and rockwool products to original equipment manufacturers (OEMs). Bradford insulation is used for acoustic or thermal purposes, and adds value to OEMs products. Glasswool can be used for the following requirements: Thermal. Acoustic. Fire resistance. CSR Bradford Insulation supplies many OEMs, and each has unique requirements for rockwool and glasswool insulation products. OEMs should contact the CSR Bradford Insulation Office in their region to discuss their specific requirements. Products. Bradford Rockwool. Bradford Glasswool. References. 1 Sound Research Laboratories, Noise Control in Building Services, Pergamon Press, First Edition Bruel & Kjaer, Noise Control, Principles & Practice, Naerum Offset, Second Edition, D.A Bies & Hansen, Engineering Noise Control, E & FN Spon, Second Edition, L.L Beranek, Noise And Vibration Control, Institute of Noise Control, Revised Edition,

54 APPENDIX A. The Nature of Sound. Introduction. For most of us, sound is simply something we hear. It is the sensation which results from vibrations in the air interacting with the hearing mechanism of our ears. Noise is by definition, unwanted sound. It may be unwanted because it is damaging, dangerous, annoying, or detracts from wanted sounds. Sound is also used as a general term to describe the vibrations or pressure variations which give rise to the sound we hear. Throughout this guide, sound will be used in the general sense. Sound moves through the air as a longitudinal pressure wave. These waves are caused either by vibrating surfaces or fluctuations in air flow. The process may be illustrated by considering what happens when we listen to sound from a radio, TV set, or public address system. The loudspeaker is made to vibrate by an electrical signal. This causes a sympathetic vibration in the air as shown in Figure A1. When the air borne vibration reaches the ear drum, the reverse process applies, causing the ear drum to vibrate, stimulating the hearing system. Sound flow is described as a wave, because it is the vibration that moves through the air. Individual air particles only vibrate on the spot with no net movement. This is similar to what happens when a stone is thrown into a pool of water. Ripples move outwards through the water, but individual particles of water only move up and down as the ripples pass. This is evidenced by observing any objects floating on the pool surface, and noting that they remain stationary. Sound waves are said to be longitudinal because the movement of air particles is in the same plane as the direction of flow as shown in Figure A2(a). This is different from water waves, where the movement of water particles is perpendicular to the direction of flow as shown in Figure A2(b). Water waves are known as transverse waves. The basic characteristics of sound are discussed below. Frequency. Frequency is the rate of vibration. It has the units of Hertz (Hz) or cycles per second where a cycle is one complete vibration to and fro. The range of human hearing - the so-called audible range - extends from 20 to 20,000Hz (20kHz). In practice, few adults can hear sounds with frequencies above 15kHz, and frequencies above 10kHz are rarely significant for sound control purposes. Sound waves are not limited only to the audible range. Higher frequency sound - ultrasound - (greater than 20kHz) has many applications in medicine and industry, while lower frequency sound infrasound (lower than 20Hz) appears as undesirable structural vibrations. FIG A1. VIBRATION CREATES SOUND WAVES. Air moves towards load speaker as cone moves backwards. FIG A2. TYPES OF TRAVELLING WAVES. (a) Longitudinal Wave Direction of wave travel Vibration of particles (b) Transverse Wave Direction of wave travel Vibration of particles Air pushed away from loudspeaker as cone moves forwards. With the exception of musical notes, sounds consisting of only one frequency are extremely rare. Most of the sounds encountered in everyday life are a complex combination of many frequencies. It is totally impractical to characterise a complex sound by all its frequencies, so the concept of frequency bands is introduced. The most common of these is the octave band, which has its upper frequency band exactly double the lower band. 54

55 All frequencies between these bands are then grouped together into the octave band. An octave band is described by its centre frequency which is the geometric mean of the upper and lower bands. The octave bands used for sound measurement are listed in Table A1. TABLE A1. STANDARD FREQUENCY BANDS. Band Limit Frequency (Hz) /3 Octave Centre Frequency (Hz) Energy, Power and Intensity. Octave Band Centre Frequency (Hz) Sound waves transmit energy from a source to a receiver, e.g. from a loudspeaker to a listener s ear. In some cases this is desirable, e.g. Iistening to music. In others, the emission of sound energy indicates inefficient machine operation, and is harmful or annoying to exposed people. The rate at which a sound source emits energy is called its sound power, measured in Watts (W). The sound power range is extremely large, ranging from about 1 nanowatt (1 x 10-9 W or W) for rustling leaves to well over 1 megawatt (10 6 W or 1,000,000 W) for violent explosions. This range of over W is difficult to handle, so a more suitable scale has been devised. This scale is the Sound Power Level scale which measures sound power logarithmically. This is especially appropriate, as the human ear responds to ratio changes in sound power, rather than to magnitude changes. To the ear, a change from 10 Watts to 1 Watt is equivalent to a change from 1 Watt to 0.1 Watt The Sound Power Level is generally denoted Lw. Abbreviations such as SWL or PWL are also used. It is defined as: Equation Nº1 L w = and expressed in decibels (db) A Sound Power of 10 Watts therefore has a sound power level of: L w = = 10 log = 130dB Similarly, a sound power of 1 Watt corresponds to a sound power level of 120dB, and a sound power of 1 milliwatt corresponds to a sound power level of 90dB. Intensity is a measure of sound power flow per unit area and is expressed in units of Watts per square metre (W/m 2 ). It is sound intensity at the ear which determines how loud a particular noise seems the greater the intensity, the louder the noise heard. Sound Pressure. Sound intensity cannot be directly measured. However, sound intensity is related to sound pressure (which is easily measured) according to Equation Nº2. Equation Nº2 I = 10 log log 10 p 2 z Sound power source (W) Reference power (1 x W) 10 1 x W Where: I = Intensity. p = Pressure due to sound wave. z = ρc = Acoustic impedance of air. ρ = Density of air. c = Speed of sound (344 m/s). The sound pressure can be measured using a microphone which converts the pressure wave to an electrical signal that can be easily measured with a galvanometer. Instruments are built specially for this purpose and are known as Sound Level Meters. 55

56 Like sound power, sound pressure is expressed on a logarithmic scale known as the Sound pressure level, generally denoted L p. Sometimes the abbreviation SPL is also used. Sound Pressure Level is defined as: Equation Nº3 L p = 20 log sound pressure (measured in Pa) Reference sound pressure (2 x 10-5 Pa) and, like sound power level, is expressed in decibels (db). The reference sound pressure of 2x10-5 Pa represents the threshold of hearing. Thus a sound pressure level of 0dB indicates the quietest sound likely to be detected by young, healthy ears. At the other end of the scale, a sound pressure level of 130dB (a sound pressure of 63 Pa) represents the threshold of pain. Some typical sound pressure levels are shown in Table 2. TABLE A2. TYPICAL SOUND PRESSURE LEVELS. Noise Source Sound Pressure Level (db re 20 µpa) Near Air Force Jet at take off 140 (Threshold of pain) 130 Pneumatic chisel 120 Angle grinding metal 110 Electric train crossing bridge 100 Petrol lawn mower 90 Average road traffic 80 Ringing telephone 70 Conversational speech 60 Analytical laboratory 50 Professional office 40 Residential area at night 30 Rustle of leaves 20 Breathing 10 (Threshold of hearing) 0 The sound pressure level then is used as the basic measure of quantity of sound. Levels can be measured right across the whole audible frequency range or in discrete octave or third-octave bands. Weighted sound pressure levels may also be measured, of which the most common is the A weighted sound pressure level. A weighting adjusts the sound pressure to allow for the frequency response of the human ear. The ear is less sensitive to lower frequencies than to frequencies in the middle to high range. A weighting therefore decreases the level of low frequency sounds relative to middle and high frequency sounds. Sound pressure levels measured with an A weighting network are expressed in A weighted decibels or db(a). Because the A weighted sound pressure levels takes account of the ear s sensitivity to sound, most noise control legislation is written in terms of db(a) levels. Where noise levels fluctuate markedly with time (such as stamping machines, traffic on a busy roadway, etc.) it is now common to measure an equivalent continuous sound pressure level, denoted L eq. This is the sound pressure level of a steady sound which, over a given time period, would have conveyed the same acoustic energy as did the time-varying sound. Many sound level meters are able to automatically measure equivalent sound pressure level. Other measures of sound level that are applicable to long-term variable noise (such as motor traffic) are denoted L x where x is a number between 1 and 100. This is the sound pressure level which is exceeded for x% of the time. The L 1, L 10, L 50 and L 90 levels are the most commonly encountered. These statistical levels can be measured with more sophisticated portable sound level meters. Alternatively, statistical analysis or graphical techniques can be used to determine the statistical levels. Addition of Decibels. As the decibel scale is logarithmic, two noise levels L p1 and L p2 values cannot be added in the same way as ordinary numbers. Consider for example, the sound power level of two machines, each with a sound power level of 120dB. From Equation Nº1 it can be calculated that the actual sound power of each source is 1 Watt. Thus their combined power will be 2 Watts which, according to Equation Nº1, corresponds to 123dB. Doubling the sound power results in an increase of 3dB in the sound power level. Adding a third machine of the same power would increase the total sound power to 3 Watts, which gives a sound power level of 125dB, while a fourth machine bringing the total sound power to 4 Watts would increase the sound power level to 126dB. Note again that doubling the sound power from 2 Watts to 4 Watts also increased the sound power level by 3dB (123dB to 126dB). This may seem complicated but there is a simple rule of thumb which is sufficiently accurate for all practical purposes: 56

57 Difference between noise levels ACOUSTIC DESIGN GUIDE Add to higher level (db) 0 or or to or more 0 For the example above, 120dB + 120dB 0dB difference Add 3dB to 120dB = 123dB 123dB + 120dB Add 2dB to 123dB 3dB difference = 125dB FIG A3. BEHAVIOUR AT SOLID BOUNDARIES. Reflected Sound Incident Sound Reflected Sound Absorbed Sound Transmitted Sound Transmitted Sound 125dB + 120dB Add 1dB to 125dB 5dB difference = 126dB Behaviour of Sound. Sound from a theoretical point source will radiate equally in all directions. As a result, the sound intensity will be inversely proportional to the square of the distance from the source. This means the sound pressure level will reduce by 6dB for each doubling of distance from the source. This generally applies outdoors in the free field. Thus, if L p = 80dB at 4 metres from the source, it will be 74dB at 8 metres, 68dB at 16 metres, 62dB at 32 metres, as shown in Figure A2. This assumes that there is no interference with the sound flow such as buildings etc, and the further one gets from the source the more likely it is that some interference will occur. The most common interference is provided by a solid boundary. Sound striking a solid boundary may be either transmitted, reflected, or absorbed, as shown in Figure A3. FIG A2. SOUND RADIATION FROM POINT SOURCE. Sound Transmission. Sound striking a solid surface can cause the surface to vibrate, just as the ear drum vibrates when it is met by a sound wave. This vibration which is of the same frequency as the sound wave may set up another air-borne sound wave on the other side of the solid. The ability of a solid structure to resist sound transmission is called acoustic insulation. This is analogous to thermal insulation being the ability of a material to resist heat flow and electrical insulation being the ability to resist the flow of electricity. It is important to note that the mechanism involved in resisting these various flows is not universal. The fact that a material is a good thermal insulation does not indicate whether it is of any use as an electrical or acoustic insulator. Acoustic insulation is expressed as the difference in decibels between the sound pressure levels on the source and receiving sides of the structure. When discussing the performance of building elements, acoustic insulation is referred to in terms of sound transmission loss (STL) or sound reduction index. For all practical building elements, the sound transmission loss varies with frequency (Figure A5). There are essentially three modes: 1. At very low frequencies the sound reduction depends on the stiffness of the partition and natural resonances in the structure. The stiffer the panel, the more resistant it is to bending. As the frequency increases, the stiffness effect diminishes and the onset of resonances occur in the panel which lowers the acoustic performance of the panel. 57

58 2. At mid frequencies sound reduction increases by approximately 6dB for each doubling of frequency (6dB per octave) or mass per unit area. 3. At high frequencies sound transmission is influenced by the coincidence dip, which is a form of coupling between the sound waves in the air and the bending waves in the panel, resulting in efficient transfer of sound energy. The coincidence effect is a form of resonance which occurs at the critical frequency and tends to reduce the acoustic performance of the building element. Transmission Loss FIG A4. TYPICAL SOUND TRANSMISSION LOSS CHARACTERISTIC FOR BUILDING PARTITIONS. Stiffness controlled Resonances 6dB per octave Mass controlled Frequency Hz Coincidence Dip Critical frequency The frequency at which this coincidence occurs is called the critical frequency, and is a function of the particular materials used in the partition. Sound transmission loss depends heavily on the surface density (mass per square metre of surface) of a building element. For every doubling of surface density the sound transmission loss increases by about 5.6dB. This is known as the Mass Law and is shown graphically in Figure A5. Higher transmission losses than those expected by the Mass Law can be obtained by using double-leaf structures, such as stud walls. Further improvement can be achieved by using wide cavities, which is not always practical. Significant transmission loss gains are obtained by using insulation such as Bradford Rockwool or Glasswool in the cavity. The sound transmission loss of a building element may be expressed as the decibel reduction in sound pressure level measured at the standard one-third (1/3) octave frequency bands. A more convenient means of expressing sound transmission loss is by use of a single number acoustic rating called Sound Transmission Class (STC). This rating system is described in detail in AS : Methods for Determination of Sound Transmission Class and Noise Isolation Class of Building Partitions. The Average Sound Transmission Loss (db) FIG A5. THE MASS LAW OF SOUND INSULATION Surface Density (kg/m 2 ) recently released AS/NZS1276.1:1999 Acoustics - Rating of Sound Insulation in Buildings and of Building Elements, Part Airborne Sound Insulation refers to Weighted Sound Reduction Index (R w ) instead of the commonly used STC. STC is derived from sound transmission loss measurements over 16 test frequency bands between 125Hz and 4000Hz. R w is calculated from frequencies ranging from 100Hz to 3150Hz. R w is considered numerically equivalent to STC, but can vary by about 1 point. A noise reduction of 1dB (decibel) is approximately equal to a 1 STC or 1 R w. Note this does not apply to lower frequency sound sources. The higher the STC or R w of a partition the more effective it will be at reducing sound transmission A reduction of 3dB in noise level is a noticeable improvement, and a 10dB reduction in noise level is perceived as being half as loud. Some STC examples are given below. 2 layers 16mm Gyprock each side of 64 mm steel studs STC = 47 As above + 75mm GW batts STC = 57 Double Brick Wall 250 mm STC = 54 Brick Wall single layer 110mm STC = 44 Sheet steel 0.8mm thick STC = 27 Aluminium window 5 mm glass STC = 22 58

59 Flanking Paths. Noise will always take the easiest path around a barrier under question. This is known as flanking. Consider noise to be like a liquid that can pass through small openings. Flanking can severely reduce the theoretical sound transmission loss of a building element. Air borne sound control is limited by flanking transmission paths which permit sound to bypass the barrier. Some of the more common flanking transmission paths are shown in Figure A6. FIG A6. COMMON FLANKING TRANSMISSIONS PATH. 1. Ceiling plenums, floors, walls. 2. Poor seals between structural elements and around service penetrations. 3. External air-borne paths. 4. Heating and ventilation ducting. 5. Rigid plumbing connections and penetrations. 6. Back-to-back cabinets and switches/power outlets. As the required performance of the wall or ceiling system increases eg. for systems over STC 45, attention to sealing of gaps to stop noise leaks is critical. Even very small gaps will derate performance significantly. Flanking can be a limiting factor in achieving the higher STC ratings for building elements in the field, especially for STC ratings greater than 55. STC ratings measured in the laboratory are usually higher than what is achieved in the field. Designers and specifiers of building facades need to be aware that in the field, flanking of noise at doors, windows, ventilation ducting, air gaps at ceiling, wall and floor intersections, and poor workmanship may result in lower acoustic STC performance. For these reasons CSR Bradford Insulation cannot guarantee the field STC ratings of specific construction shown in this Acoustic Design Guide and other CSR Bradford Insulation brochures. Maximum sound transmission loss can be achieved by eliminating penetrations in walls, caulking gaps, and staggering electrical outlet or other necessary penetrations through the wall. For optimum acoustic performance, wall cavities should be filled with either rockwool or glasswool insulation. Pipes, conduits and other outlets should have insulation tightly fitted around them. Sound Reflection. Sound may also be reflected from a solid surface in much the same way as a ball bounces from a wall. Reflected sound will increase the sound level on the source side of the solid. The most common example of this is a noise source such as a machine located above a hard concrete floor. Sound will radiate equally in all directions from the machine. However, sound travelling downwards will strike the floor and be reflected upwards as shown in Figure A7. The sound level above the floor will be the sum of both the direct sound and the reflected sound. Sound Absorption. Sound may also be absorbed by the solid. The acoustic energy is converted to heat energy as a result of frictional forces within the solid. Large amounts of sound may be absorbed with little effect on the temperature of the absorbing material. Most hard solid surfaces are highly sound reflective. Open cell or porous materials are the most effective sound absorbers. The long, narrow, twisting air paths give rise to considerable friction between vibrating air particles and the fibres or cell walls. The friction converts much of the sound energy into heat and the process is referred to as sound absorption. Increasing the thickness or density of a porous material will increase its sound absorption. Increasing the thickness is the most effective method of increasing the sound absorption of a material, particularly at the lower frequencies. A material s ability to absorb sound is expressed by its sound absorption coefficient, which is sometimes denoted by α and defined as: α = ( Sound energy reflected from surface) 1 Sound energy incident on surface The sound absorption coefficient is reported as a decimal, e.g. α = 0.75 would mean that 75% of the incident sound energy was absorbed while 25% was reflected. A more convenient method of describing sound absorption is to use the single number NRC (Noise Reduction Coefficient). NRC is the arithmetic average of the sound absorption coefficients at the four frequency of 250Hz, 500Hz, 1000Hz and 2000Hz. NRC is usually rounded to the nearest 0.05 as per Australian Standard AS1045 : 1988 Acoustics - Measurement of Sound Absorption in a Reverberation Room. 59

60 For many porous absorbers such as rockwool and glasswool, sound absorption coefficients or NRCs are commonly greater than For example: 75mm thick Bradford Glasswool Supertel (32kg/m 3 ) NRC = mm thick Bradford Fibertex 350 Rockwool (60kg/m 3 ) NRC = 1.05 Although it is theoretically impossible to have sound absorption coefficients greater than 1, as this would mean that more sound is absorbed by the material than is incident on it, NRCs greater than 1 do occur in laboratory testing as a result of the measuring techniques and the sound field within the testing facility. Sound absorption coefficients are measured on a linear scale and so do not relate directly to decibels. The effect of sound absorption on sound pressure level is discussed under Reverberation Control. Sound absorption materials do not absorb equal amounts of sound in all frequencies. Thus it is necessary to determine the sound absorption coefficient for each octave band, or more preferably for each one third octave band. The sound absorption coefficients of some typical building materials are listed in Table A3. Sound absorption coefficients may be determined in an acoustic laboratory by two different methods. The simplest of these uses a device called an impedance tube and its use is covered by AS/NZS1935 Acoustics Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes. A more involved method uses a specifically constructed room known as a reverberation room. This method is set down in AS1045 : 1988 Acoustics Measurement Of Sound Absorption Coefficients In A Reverberation Room. The impedance tube method being simpler, and therefore cheaper, has been favoured by some manufacturers of acoustic products. It has a major limitation however in that it only allows for normal incidence of sound as shown in Figure A8(a). In practice, sound will impinge on the sound absorbent material from all directions. TABLE A3. TYPICAL VALUES OF SOUND ABSORPTION COEFFICIENTS. Typical Building Materials Frequency (Hz) NRC Reflective Sound Absorption Coefficients (α) Terrazzo Flooring on concrete Concrete 100mm Exposed Brick Fibrous Cement Timber Floor Plasterboard Glass window 4mm Hardboard Suspended Plasterboard Ceiling Aerated lightweight concrete Absorptive Thick Pile Carpet Open Cell Polyurethane Foam 25mm Polyester 25mm Perforated Metal Pan Ceiling with Glasswool backing Bradford Flexitel Glasswool 25mm Bradford Supertel Glasswool 50mm Bradford 50mm Fibertex 350 Rockwool Refer to Appendix C for Sound Absorption Coefficients of Bradford Insulation products. 60

61 The reverberation room allows for this random incidence as shown in Figure A8(b). For some applications such as ceilings and air conditioning ducts or glazing, glancing incidence as shown in Figure A8(c) predominates. As can easily be seen, data obtained by using normal sound incidence will be totally inappropriate for evaluating performance in glancing incidence situations. It is important therefore to check by which method, published sound absorption coefficients have been determined. All leading Australian manufacturers publish data measured in accordance with AS Acoustics Measurements of Sound Absorption in a Reverberation Room. Some imported products may claim performance on the basis of overseas standards. Such performance data is not necessarily in accordance with the Australian standard. Sound Source FIG A7. DIRECT AND REFLECTED SOUND. Direct Sound Reflected Sound FIG A8. TYPES OF SOUND INCIDENCE. (a) (b) (c) Normal Incidence Random Incidence Glancing Incidence Sound absorption coefficients may also be calculated empirically from the flow resistivity of porous or fibrous absorbers. The flow resistivity is usually measured by an American Standard test method, ASTM C522-73, as there is no Australian Standard for this test. The use of flow resistivity data enables prediction of the sound absorption coefficients for composite materials and thus minimises the number of laboratory tests required. As with all empirical calculations, predictions should be compared to actual test data to ensure the validity of the calculations. Fibrous materials such as Bradford Rockwool and Glasswool are extremely efficient absorbers of sound at mid to high frequencies. Low frequency absorption is influenced by the thickness of the material. The sound absorption coefficients of Bradford Rockwool and Glasswool products are shown in Appendix C of this guide. Further improvement in low frequency sound absorption may be achieved by using Bradford Rockwool or Glasswool thicknesses greater than 50mm or by using an air space behind. For optimum acoustic absorption particularly at low frequencies, the air space should be at least as thick as the rockwool or glasswool insulation. The sound absorption for a surface is the product of the sound absorption coefficient and the area of the surface. The unit is the Sabin, where 1 Sabin is the amount of absorption provided by 1 square metre of surface with an absorption coefficient of 1. There is a trend to replace the Sabin with equivalent absorption area. The calculation is still the same, however units of square metres are used. Reverberation. When sound is produced within an enclosed space such as a room, the first sound which a listener hears is that which arrives directly from the source. The next sound to be heard will be that which has been reflected from one wall of the enclosure. After this, sound which has been reflected from two, three, or more surfaces will successively arrive. These multiple reflected or reverberant sounds combine with each other and the direct sound to form the resulting sound field as shown in Figure A9. Not only does the reverberant sound increase the level of sound, it also increases its duration. This causes distortion of the sound with particularly detrimental effects on speech and music. When long delays occur between the arrival of direct and reflected sound, distinct echoes can be heard. Sound can take 2 paths in a room: the direct sound and the reflected sound. The total sound level is the sum of the direct and reflected sounds. The reflected sound will lose energy when striking the boundaries of the room. Some of this reflected sound will be transmitted and some absorbed, so that the amount of sound reflected will be less than that striking the boundary. For a continuous noise source, a steady-state situation will develop where the rate of sound energy entering the room from the noise source will be balanced by the rate of sound energy leaving the room by transmission and absorption. 61

62 FIG A9. DEVELOPMENT OF REVERBERANT SOUND. TABLE A4. OPTIMUM REVERBERATION TIMES. Room Reverberation Typical Example Acoustics Time (sec) Dead 0.6 Hotel and airport lounges, Surgeries and consulting Rooms, Kindergarten. Sound Source Medium Dead Classrooms, Restaurant, Large open-plan offices. Medium Lecture rooms, General Offices, Hospital Wards. Direct Sound = Reflected Sound = REVERBERATION TIME. Reverberation Time (RT) is the time it takes a sound to travel from its source to and from reflecting surfaces and gradually become inaudible. More technically speaking, RT 60 is the time taken for the reverberant sound pressure level to decrease by 60dB after the direct sound has ceased. The reverberation time of any room depends primarily upon the degree of sound reflection from the room boundaries and objects within the room. The more reflective surfaces in the room, the longer will be the reverberation time. Room dimensions also have an effect. As sound levels fall due to absorption and transmission at solid boundaries, it follows that where sound has to travel further between reflections (ie larger rooms), it will take longer for the sound pressure level to fall, resulting in longer reverberation times. Rooms used for different purposes need different reverberation times. Churches, concert halls and music studios may require reverberation times of up to 2 or 3 seconds, while for broadcasting studios and open plan offices appropriate reverberation times may be below 0.5 seconds. Reverberation time affects both the room acoustics and the noise level. Short reverberation times result in lower noise levels and what is commonly called dead acoustics, while long reverberation times result in higher noise level, or live acoustics. For everyday purposes, reverberation time criteria can be classified as shown in Table A4. The optimum reverberation time depends upon the intended use of the room. Medium Live Board Rooms, Conference Rooms, Assembly Halls. Live 1.4 Music Rooms, Concert Halls. Figure A10 from Australian Standard AS2107 : 1987 shows optimum reverberation times for various rooms. Reverberation times are usually quoted for frequency of 500Hz or 1kHz. Ideally, the reverberation time at higher frequencies should be the same as that at 500Hz, but in practice some reduction in reverberation time at frequencies above 2000Hz is almost inevitable. For good music listening condition the reverberations time at frequencies below 500Hz should increase while for speech there should be little deviation from the value at 500Hz. REVERBERATION CONTROL. Increasing the amount of sound absorption within a room reduces both the reverberant sound pressure level and the reverberation time. The effect on reverberant sound pressure level is a 3dB reduction for each doubling of absorption. Thus, in a highly reflective room the addition of small amounts of sound absorbing materials will have a marked effect on the sound pressure level, while in a highly absorptive room the addition of large amounts of sound absorbing materials may have little effect. Reverberation control as a means of noise control is limited by two factors. Firstly, it is not possible to reduce the total sound pressure level below that due to direct air borne sound transmission from source to receiver. Secondly, very large amounts of sound absorption may make the room unacceptably dead by reducing the reverberation time too much. The reverberation time depends on the room volume and the total sound absorption present in the room. It may be calculated by: 62

63 3.0 FIG A10. MEAN REVERBERATION TIMES (FROM AS2107 : 1987). Midfrequency Reverberation Time (sec) Speech Studios Churches Music Studios and Concert Halls Speech Auditoriums Variety Entertainment Theatres Film and TV Studios Opera Houses Room Volume (m 3 ) Equation Nº5 T = V A Where: T = reverberation time (sec) V = room volume (m 3 ) A = Sα total absorption (Sabins) Where: S = room surface area (m 2 ) α = average sound absorption coefficient for room surfaces Note: Equation Nº5 shows that doubling the amount of absorption in the room halves the reverberation time. For highly sound absorbent rooms such as recording studios, the reverberation time is more correctly calculated by: Equation Nº6 T = V S ln (1 α) The use of CSR Bradford Rockwool or Glasswool insulation is the most effective means of absorbing sound and reducing overall sound levels in enclosed areas. 63

64 Room Acoustics. While legislation sets noise limits for industrial exposure, it is left to the architect or consultant to set appropriate noise levels for rooms. The Standards Association of Australia provides a comprehensive list of recommendations in AS2107 : 1987 Acoustics - Recommended Design Sound Levels and Reverberation Times for Building Interiors. A guide to suitable background sound levels is given in Table A5. TABLE A5. RECOMMEND MAXIMUM BACKGROUND NOISE LEVELS. Type of Activity Recommended Ambient Sound Level db(a) Board and conference rooms Computer rooms General office areas Private offices Small retail stores Supermarkets Hotel lounges Libraries - reading areas Restaurants Airport lounges Places of worship Court rooms Surgery and consulting rooms Hospital wards Classrooms Laboratories - Teaching Laboratories - Working Lecture theatres - up to 250 seats Lecture theatres - more than 250 seats Bowling alleys Squash courts REVERBERATION CONTROL IN BUILDINGS. Hard surfaces are excellent reflectors of sound which magnifies the effect of the initial noise source. Where the overall noise level depends mainly on a build-up of reflected sound within the room, a significant reduction in noise level may be achieved by increasing the total sound absorption in the room. This may be achieved most simply by using absorptive rather than reflective materials at room boundaries. Increasing the sound absorption within a room will also reduce its reverberation time. In most cases this will be desirable as a high level of reflected noise generally indicates excessive reverberation time. The reverberation time should not be shortened too much as it would make the room unnaturally dead for the purpose for which it is used. However if the space contains unwanted noise, maximum absorption is desirable. Sound Absorption Coefficient (α) FIG A11. SOUND ABSORPTION OF DIFFERENT TYPES OF ABSORBERS. Cavity Absorber Dissipative Absorber Membrane Absorber Frequency (Hz) Absorbing or controlling noise within a space can be done using materials called sound absorbers which can be grouped into 3 categories; porous or dissipative absorbers, membrane or panel absorbers and cavity absorbers (see Figure A11). 64

65 POROUS OR DISSIPATIVE ABSORBERS. Porous or dissipative absorbers, (eg. rockwool or glasswool insulation) which work by converting sound energy from the moving air particles into heat through friction. This occurs in the material s many tiny narrow fibrous airways. The thicker and denser the porous absorber is, the better the sound absorption. (Refer to Figure A12). Porous absorbers are often faced for support and/or decorated with: Perforated facings - foil, metals (such as Bradford Acousticlad), timber or plasterboard. Bradford Ultraphon, Black tissue facing, Thin polyester film or Fabrics. FIG A12. POROUS ABSORBERS EFFECT OF THICKNESS. FIG A13. BROAD-BAND SOUND ABSORBER. Plan View. Wall Bradford Glasswool or Fibertex Rockwool Chicken Wire Gyprock plasterboard, perforated hardboard, expanded metal or Bradford Thermofoil HD Perforated Wall Airspace should be at least the thickness of the cavity insulation FIG A14. TIMBER PANELLING FOR LOW FREQUENCY ABSORPTION. Plan View. Timber Framing Bradford Glasswool Building Blanket or Fibertex Rockwool Timber Panelling Timber Batten Random Incidence Absorption Coefficient (x) mm Thickness 25mm Thickness 12mm Thickness 6mm Thickness Freqencey (Hz) Absorption (%) CAVITY ABSORBERS. Cavity absorbers are usually an enclosed volume of air with a small neck opening. The moving air particles produce a type of pumping action in the neck of the cavity, converting the sound energy into heat. Most common type of cavity absorber is a Helmholtz resonator. Cavity absorbers provide a very narrow band of sound absorption, which can be expanded with the use of rockwool or glasswool insulation in the enclosed space. These absorbers have specialised acoustic applications such as studios and auditoria and for pure tone absorption. The excellent sound absorbing properties of Bradford Rockwool and Glasswool can be used to great advantage in reverberation control. MEMBRANE OR PANEL ABSORBERS. Sound is transferred into vibrational energy in the face of the panel with maximum absorption occurring at the resonant frequency of the panel (see Figure A13). The resonant frequency is affected by surface density of the panel, the size and stiffness of the airspace behind the panel and the spacing of the panel supports. As the airspace or mass of the panel are increased, the frequency of maximum absorption, (ie. the resonant frequency) decreases. Adding rockwool or glasswool insulation in the air cavity of panel absorbers, increase their absorptive frequency range. Typical examples are solid, reflective panels (timber, plasterboard etc.) panel on studwork, lightweight partitions on studwork, suspended ceilings and windows. REVERBERATION CONTROL IN BUILDINGS. Some typical examples include: UNDER-ROOF. Where condensation protection is required, install Bradford Anticon or Acousticon with foil facing under the steel roof. For better acoustic absorption, install 50mm to 100mm Bradford Fibertex Rockwool or Bradford Glasswool (Flexitel, Supertel or Ultratel ) blanket faced with CSR Bradford Thermoplast 980 perforated foil. This is an effective way to add significant sound absorptive insulation. 65

66 FIG A15. ABSORPTIVE WALL TREATMENT IN SCHOOL HALL. Black Matt Faced FIBERTEX Retained Behind Spaced Timber Strips. SUSPENDED BAFFLES. An alternative treatment which maximises absorptive area is to install Bradford Rockwool Acoustic Baffles. Baffles may be installed at any height and do not need to be all in the same plane. A regular pattern is most easily installed using a suspended ceiling grid. Inverted aluminium U-channels are fixed to the underside of the grid. The baffles are then secured to the U-channel using self tapping screws. Alternatively, individual baffles may be suspended using galvanised wire and S hooks. CEILINGS. The use of black-faced Bradford Glasswool Blanket as an acoustic overlay for slatted timber, metal strip, and perforated metal pan ceilings is illustrated in Figure A15. The non-reflective black finish significantly enhances the appearance of these ceilings while the glasswool absorbs noise that would otherwise be reflected back into the room. An alternative approach is to use a fully exposed metal suspension grid to support the ceiling which also achieves an air gap behind the batts to boost low frequency sound absorption. WALLS. Sound absorbing walls may be constructed by retaining rockwool or glasswool behind spaced timber panels as shown in Figure A15. Alternative treatments include fixing the sound absorbing batts behind perforated plywood, perforated Gyprock plasterboard or metal. The use of a black matt tissue finish or Bradford Ultraphon on the batts is recommended for aesthetic reasons. Sound absorbing panels may also be fixed to walls as shown in Figure A17. The decorative facing chosen should be acoustically transparent (with low flow resistance) to maximise the amount of sound reaching the insulation behind. Open weave fabrics are suitable for these applications. FIG A17. ABSORPTIVE WALL PANELLING RIGID BOARD WITH DECORATIVE FACING. FIG A16. SOUND ABSORPTIVE TREATMENT OF METAL PAN CEILING. 66

67 TABLE A6. INSULATION FOR NOISE REVERBERATION CONTROL. Application Product Comment Sports/Community Centre Bradford Glasswool Blanket faced with Cost effect way to add large Walls/Roof. Thermoplast 980 Perforated Foil. quantity of absorption. Insulation over Perforated Bradford Glasswool Blanket BMF High absorption capacity Plasterboard or Perforated Metal. or Flexitel BMF/Ultraphon. enhanced by air space behind ceiling. Absorption Behind Cinema Screens. Bradford Supertel BMF/Ultraphon Optimum sound absorption over all frequencies. Cinema Wall. Bradford Supertel or Ultratel - Absorptive and Front Runner faced. aesthetic facing. Bottling/Canner Plant. Bradford Acoustic Baffles. Convenient way to add absorption to reverberant areas where conventional methods are not available. Acoustic Enclosure. Bradford Acousticlad For industrial noise control (Fibertex Perforated Metal). Fibertex Rockwool products are excellent acoustic absorbers. Sound Recording Studio. Bradford Fibertex 350 Rockwool For high level of sound BMF or Ultraphon faced or absorption at low frequencies, Bradford Glasswool Ultratel use 100mm thickness. Conference Room. Bradford Ductel faced. High absorption with with front runner compression resistance and aesthetic surface. BMF = Black Matt Facing Industrial Acoustic Design Criteria. Industrial noise is a by-product of the mechanical age. Its nuisance value has long been tolerated as an unavoidable consequence of labour-saving plant and equipment. But we now know that excessive noise is not just annoying - it is also dangerous. It causes both temporary and permanent hearing damage, body fatigue, nervous stress, and adversely affects workplace safety by masking communication and warning signals. Hearing loss cannot be cured. It is now generally accepted that continued exposure to noise levels of 80dB(A) or more will result in hearing loss. Already researchers are suggesting the danger level may be even lower. The increasing number of people suffering from noise induced hearing loss underlines the importance of controlling noise in factories. Noise levels can be reduced and excessive noise should no longer be considered an occupational hazard. Some of the many means by which noise can be controlled will be discussed in this brochure. The costs of noise control may appear high, especially when correcting existing problems, but the costs of workers compensation, non-compliance with legislation, and industrial disharmony, in the long term, can be much more expensive. The fatiguing aspects of noise may lead to lowered productivity and the cost of this in an ongoing situation is also high. NOISE LEVELS. The first criterion considered here is usually noise legislation. There are essentially two components: (i) the noise level to which employees may be exposed, i.e. Occupational Noise. (ii) the noise level that the factory may emit to the surrounding community. In Australia The NSW Occupational Health & Safety Regulation 1996 (effective 31 May 1997) states a place of work is unsafe and a risk to health if any person is exposed to noise levels : 67

68 a) that exceed an 8 hour noise level equivalent of 85dB(A) or b) Peak noise levels of 140dB (Lin) or more. For every 3dB(A) above 85dB(A), the exposure time is halved, so that four hours exposure would be permitted at 88dB(A) and two hours at 91dB(A) and so on. Conversely, every 3dB(A) lowering of the noise levels doubles the time for which employees may be exposed. Therefore 16 hours of exposure would permitted at 82dB(A). Compliance with noise legislation does not therefore automatically ensure that employees will not suffer noise induced hearing loss. Permitted noise emission levels depend upon the location of the factory and it s proximity to residences/offices nearby. The Environment Protection Authority (EPA) sets noise criteria for noise emissions from industry. The character of the noise is also important. High frequency sounds are more annoying than sounds of low frequency, while noise with prominent tonal components is more annoying than broad band noise of the same intensity. The hours of operation also affect the permitted noise emission levels. Lower levels apply at night than during the day. Other aspects affected by noise level include: SPEECH INTELLIGIBILITY. High noise levels above 70dB(A) can make verbal communication extremely difficult and loss of speech intelligibility can occur. This leads to misunderstandings which can result in inefficient process operations, product losses, unsafe working practices, and industrial unrest. MACHINE OPERATION. The sounds emitted by many machines convey important information to operators on the functioning of the machine. Excessive background noise may mask these sounds, preventing early detection of machine malfunction. Expensive repairs and loss of productivity may result. WARNING SIGNALS. Many warning signals or alarms rely on sound to attract people s attention. Most alarms now incorporate both visual (e.g. flashing lights) and audio signals, but it is important to note that visual signals are only effective for the line of sight, while audio signals are designed to attract attention regardless of where an employee may be looking. High background noise levels may mask these warning signals, resulting in unsafe work practices and inefficient process operation. CONCENTRATION. High noise levels are known to affect concentration which leads to increased errors in machine operation and failure to detect quality defects in product. Lack of concentration can also be a safety hazard resulting in injury to employees and equipment damage. Each situation will have its own peculiarities so it is not possible to set a universal permissible noise level for all factories. Consideration of the above factors, together with the costs involved, should permit a responsible target noise level to be set. Speech Privacy. The need to preserve confidentiality of conversation arises in many situations. Discussions in conference rooms and executive offices should not be overheard. People waiting in airport lounges or hotel lobbies wish to converse freely. Intimate diners do not wish to share their conversation with others in the restaurant. Acoustical privacy is paramount in residential situations where walls or floors abut adjoining residences. Bedrooms in one residence need to be acoustically isolated from rooms in other residences to avoid annoyance. Similarly impact noise on hard floors can irritate people in rooms below. The level of speech privacy required will depend on the particular situation. Three categories may be considered: 1. Partial coherence small portions of the conversation may be intelligible to an uninvolved listener, but he/she will not be able to follow the conversation as a whole, 2. Incoherent an uninvolved listener can hear the sound of conversation but it is not intelligible, 3. Inaudibility no sound whatever can be heard by an uninvolved listener. Speech privacy is a two-way consideration. It may be required to protect the confidentiality of conversation (eg. a boardroom meeting) or on the other hand, to avoid distraction of uninvolved listeners (eg. office workers or people in a library). Typically in commercial applications, noises such as conversations, telephones ringing etc can be heard from one office to another (also known as crosstalk ). This can cause disruption, annoyance, and decreased productivity. Crosstalk usually occurs from sound flanking via the: light weight ceilings (refer to Ceilings, page 18 for diagrams showing installation ). Air conditioning ducts (refer to Air Conditioning Noise Control, page 36). Windows and doors. 68

69 APPENDIX B. Floor/Ceiling Systems. TABLE B1. FIRE AND ACOUSTIC CEILING SYSTEMS UTILISING AND CSR GYPROCK PLASTERBOARD. Detailed information on these and alternative CSR Fire and/or Acoustic Rated Ceiling Systems and Wall Systems is published in the CSR Gyprock Fire and Acoustic Design Guide, NºGYP500. Framing Method System Fire Weighted Impact BRADFORD Insulation Material Nº Resistance Level Sound Insulation GYPROCK Plasterboard Ceiling Lining FRL R w Class CSR 800 / / 27 No insulation No plasterboard CSR 801 / / 38 R2.0 Bradford GOLD BATTS 1 x 13mm GYPROCK Plasterboard CD CSR 802 / / 42 R2.0 Bradford GOLD BATTS 2 x 13mm GYPROCK Plasterboard CD CSR /30/30 + BCA FPC 36 No insulation 1 x 13mm Gyprock FYRCHEK Plasterboard CSR /60/60 + RISF R2.0 Bradford GOLD BATTS 2 x 13mm Gyprock FYRCHEK Plasterboard CSR /60/60 + RISF R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard CSR /90/90 48 R2.0 Bradford GOLD BATTS + RISF 60 CSR /120/120 + RISF x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard CSR 811 / / 44 CSR /30/30 + BCA FPC 46 CSR /60/60 + RISF CSR /60/60 + RISF CSR /90/90 + RISF CSR /120/120 + RISF R2.0 Bradford GOLD BATTS 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard CSR 821 / / CSR 823 / / CSR 824 / / CSR /30/30 + BCA FPC CSR /60/60 + RISF CSR /60/60 + RISF CSR /90/90 + RISF RISF = Resistance to Incipient Spread of Fire. BCA FPC = Building Code of Australia Fire Protective Covering. R2.0 Bradford GOLD BATTS 1 x 13 GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 10 SOUNDCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 10 SOUNDCHEK Plasterboard R1.5 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R1.5 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R1.5 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R1.5 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard 69

70 Framing Method ACOUSTIC DESIGN GUIDE TABLE B1. (continued) System Fire Weighted Impact BRADFORD Insulation Material Nº Resistance Level Sound Insulation GYPROCK Plasterboard Ceiling Lining FRL R w Class CSR 831 / / 48 CSR 833 / / 48 CSR 832 / / 53 CSR 834 / / 53 CSR /30/30 + BCA FPC 48 CSR /60/60 + RISF CSR /60/60 + RISF CSR /90/90 + RISF CSR /120/120 + RISF R2.0 Bradford GOLD BATTS 1 x 13 GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 10 SOUNDCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 13 GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 2 x 10 SOUNDCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard CSR 841 / / CSR /30/30 + BCA FPC CSR /60/60 + RISF CSR /60/60 + RISF CSR /90/90 + RISF CSR /120/120 + RISF R2.0 Bradford GOLD BATTS 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard CSR 860 / / 50 R1.5 Bradford Glasswool ANTICON over purlins 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS on ceiling CSR /90/90 + RISF R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard CSR /60/60 + RISF CSR /90/90 + RISF CSR /60/60 + RISF CSR /90/90 + RISF R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard RISF = Resistance to Incipient Spread of Fire. BCA FPC = Building Code of Australia Fire Protective Covering. NOTE: Bradford FIBERTEX Rockwool Batts. When using Bradford FIBERTEX Rockwool Batts in the systems detailed in Table B1, R w or STC rating is generally increased by 1 to 3 units. Please refer to the CSR Bradford Insulation Acoustic Design Guide or contact your regional CSR Bradford Insulation office for more information. 70