AUDITORIUM: A CASE STUDY ON ACOUSTIC DESIGN BUILDING SCIENCE II ARC3413/BLD61303 SEMESTER 5

Transcription

1 AUDITORIUM: A CASE STUDY ON ACOUSTIC DESIGN BUILDING SCIENCE II ARC3413/BLD61303 SEMESTER 5 BACHELOR OF SCIENCE (HONS) IN ARCHITECTURE SCHOOL OF ARCHITECTURE BUILDING AND DESIGN LECTURER: MR. AZIM SULAIMAN GROUP MEMBERS: ALAN KOO CANISIUS BONG JOYCE WEE KAN SOOK SAN LIEW JIN LUM SI CHU MAXIMILIAN LIM ONG EUXUAN RICCO SOH

2 TABLE OF CONTENT INTRODUCTION..3 Historical Background - Organization - Building Auditorium DRAWINGS.6 Plans Section SOUND ABSORPTION...9 Finishing Materials - Floors - Walls - Ceilings - Seats Acoustic Wall Panelling / Treatment - Stretched Fabric Panels - Hardwood Wall Slats SOUND SOURCE..18 Sound Systems - Single Speaker Cabinets - Line Array Speakers - Stage Monitors Noise Intrusion Areas SOUND PATH / PROPOGATION 25 Sound Shadow Area Sound Reflection - Ceilings - Walls Sound Diffraction REVERBERATION TIME..33 2

3 INTRODUCTION HISTORICAL BACKGROUND 3

4 Organization: Sidang Injil Borneo Kuala Lumpur (SIBKL) As one of the most established protestant churches in Malaysia, Sidang Injil Borneo was started in Sarawak, and has been around for nearly ninety years. In 1999, SIBKL became a cell church for the Sidang Injil Borneo, and operates more than 90 cell groups for people of all ages across the region. Case Study Location: Bangunan Yin, Jalan Damansara Weekly Sunday sessions of SIBKL are carried out every Sunday in Bangunan Yin, located in Phileo Damansara, Petaling Jaya. Bangunan Yin is a multi-storey building that houses the church, as well as smaller offices during the weekdays. AUDITORIUM 4

5 SIBKL Auditorium, Bangunan Yin, Jalan Damansara Type of Auditorium: Multipurpose (Speech and Music) Shape: Fan-shaped Total Volume: m 3 Total Floor Area: 2120 sqm Year of Completion: Sunday sessions and church events are carried out in the auditorium of Bangunan Yin, located on the fifth and sixth floor of the building. The auditorium has two floors, and has a seating capacity for more than 1500 people. It has a fan-shaped balcony that hovers over the auditorium, multiplying its space, allowing the auditorium to hold more audience. 5

6 DRAWINGS Floor Plans Fifth Floor Plan of Bangunan Yin 6

7 Sixth Floor Plan of Bangunan Yin SECTIONS 7

8 Sections of Bangunan Yin 8

9 SOUND ABSORPTION Sound absorption is defined as the change in sound energy into heat energy, as the incident sound that strikes a material that is not reflected back. It is also one of the major factors in creating good acoustic space, especially when controlling reverberation. Soft and porous materials like fabrics serve as good acoustic insulators which means it absorbs most of the sound. Finishing Materials Floor 9

10 Location of carpeted floor on auditorium plans Material: Carpet (Porous Absorber) Absorption coefficient for thick pile carpet: 0.50 Carpet is the antithesis of hard, echoing surfaces. Sound waves are effectively absorbed and deflected by the carpet and by the padding under the carpet, and the level of sound absorption can be enhanced with a thicker pad. Walls 10

11 Material 1: Fabric Absorption coefficient for fabric: 0.90 The walls of the auditorium is covered with fabric wrapped wall panels. These wall panels serve to reduce echo and reverberation in the auditorium, improving the intelligibility of sound within the space. Material 2: Timber Hardwood Absorption coefficient for Belian timber hardwood: 0.42 Timber is also greatly used on wall slats in the auditorium. Its reflective nature performs strongly for acoustics. Due to internal friction within the substructure of wood, timber has a strong sound dampening capacity, allowing to control its echo and reverberation by reducing the transmission of sound vibration. Ceiling 11

12 Location of timber finishing on auditorium reflected ceiling plans Material 1: Timber Hardwood Absorption coefficient for timber hardwood: 0.42 The ceilings of the auditorium are lined with timber convex reflective surfaces. Parts of the ceilings are also comprised of strips of timber slats. Timber is reflective and has a strong sound dampening capacity. 12

13 Location of gypsum boards on auditorium reflected ceiling plans Material 2: Gypsum Board Absorption coefficient for plaster board: 0.08 Gypsum board is a plasterboard panel material. It is constructed with joints and fastener heads that will eventually be covered with a joint compound system to create a continuous surface for ceilings and walls. In the case of this auditorium, it is used to produce edges and concave surfaces that would help with the reflection of sound. 13

14 Seats Location of cushioned seatings on auditorium plans Material: Cushioned Fabric Seatings (Porous Absorber) Absorption coefficient for cushion fabric: 0.64 There is a total of 1584 cushioned seats in the auditorium (1117 seats at the bottom seating region, 467 seats on the balcony s upper seating region). To make the hearing conditions satisfactory when the room is full or partly full, upholstered seats with absorbing material at the bottom are used, so that the absence or presence of audience does not affect the reverberation time. 14

15 Acoustic Wall Panelling / Treatment This auditorium installed individual panels of slit wooden resonators that alternate between stretched fabric panels on its walls to maximize the sound absorbing quality of the space. 15

16 Stretched Fabric Panels Material 1: Stretched Fabric Panels (Membrane Absorber) These wall panels are used to reduce echo and reverberation in the auditorium. They are constructed from a rigid acoustical board, and are covered with acoustically transparent fabrics. The fabric on the panels help to reduce echo and reverberation. Advantages of fabric wrapped panel absorber: - Maximize absorption of broadband sound frequencies, from 40 Hz to 20 khz. - Reduce excessive reverberation, flutter echo and primary reflections, increasing the intelligibility of speech and clarity of sound. - Easy installation - Impact resistant, sturdy, lightweight construction - Easy maintenance 16

17 Hardwood Wall Slats Materials: Hardwood Wall Slats (Cavity Absorber) Beyond the cavities of the wall panels are narrow necks that lead down to air spaces. The enclosed body of air are contained within these rigid panels. The sound that propagates within the auditorium will be trapped in these air spaces to reduce sound reflection within the space. 17

18 SOUND SOURCE Sound source is the source of where sound waves are generated. It creates vibrations in the surrounding medium, allowing them to propagate. Generally, within an auditorium, the source of sound is usually the sound system speakers. 18

19 Sound Systems A typical sound system in an auditorium may include a combination of microphones, signal processors, amplifiers and loudspeakers in speaker cabinets. These systems reinforce sound to enhance its volume, then distribute it to a larger audience. 19

20 The sound system in the auditorium is controlled by an audio mixing board that makes live sounds louder, and also distributes those sounds to a wider audience. It may also enhance or add effects the sound of the sources on stage. 20

21 Single Speaker Cabinets Single Speaker Cabinets ultimately reproduces tone as sound waves in the air which are what reaches the listener s ear, or a studio microphone. Position of speaker cabinets on auditorium plan There are 8 speakers placed at the front of the stage. Instead of placing them on the floor, the speakers are placed elevated on stage platform so that the high frequencies project over the heads of the audience members closest to the stage. 2 of the speakers are placed slanted to the left and right to balance the sound waves in the auditorium. 21

22 Line Array Speakers A line array speaker is a loudspeaker system that is made up of a number of usually identical loudspeaker elements mounted in a line. The distance between adjacent drivers is close enough that they constructively interfere with each other to send sound waves with a more evenly distributed sound output pattern. Position of speakers There are 2 of these speakers placed in the hanging position above the stage on the left and right. These speakers are curved with the bottom part angled down to provide extra coverage at locations close to the front of stage, where else the top half will be angled upwards towards the audience at the top mezzanine floor of the auditorium. 22

23 Stage Monitor Speakers A stage monitor is a type of speaker used on stage in auditoriums and halls where accurate audio reproduction is crucial. These speakers help amplify the sound when acoustic instruments or voice are used, allowing the performers on stage to hear themselves. Position of studio monitors on auditorium plan There are 2 of these speakers placed in front of the stage by the stairs. They are placed on the ground, allowing it to project sound towards the stage, helping musicians on stage to focus and monitor the audio, allowing acoustic instruments and vocals to be heard over electronic instruments and drums. 23

24 Possible Noise Intrusions Noise intrusion on fifth floor plan The possible noises that could affect the auditorium is the lift lobby and the auditorium lobby where guests and users gather or enter the auditorium. Noise intrusion on sixth floor plan The other possible noises could be from the lobby of the mezzanine floor where people gather or first enter the auditorium. 24

25 SOUND PROPAGATION Sound propagation (or sound path) shows the movement of sound traveling. During the propagation of sound, these sound waves can be reflected, refracted, diffracted, or attentuated by the medium. 25

26 Sound path in section Sound path in plan 26

27 Sound Shadow Area Sound shadow is an acoustic defect where an area through which sound waves fail to propagate. The sound shadow area in this auditorium is the seating area located under the balcony. Sound shadow area shown in section The balcony cantilevers over the seating area on the fifth floor of the building, making the jutted out structure a obstruction, blocking sound waves from entering the region. 27

28 Solution Single speakers are added on the ceiling at the bottom of the balcony, projecting sound towards the audience in the sound shadow area, preventing sound shadowing, thus allowing them to receive the sound waves. Location of additional single speakers in floor plan and reflected ceiling plan Sound shadow area solved shown in section 28

29 Sound Reflection Sound reflection occurs when a wave reaches the boundary between objects, part of the waves undergoes reflection and another part undergoes transmission across the boundary. Despite he fact that auditoriums typically avoid using hard and smooth materials in the construction of their inside halls, these reflective surfaces may still be of use to distribute and reinforce sound. Ceilings Tilted Ceiling The ceiling of the auditorium is irregular, and properly tilted to allow more useful reflection of sound. As opposed to a flat ceiling, the range of useful ceiling reflections is wider. Tilted ceiling in section 29

30 Convex Surfaces Sound is reflected on hard surfaces in the auditorium. They tend to reflect off flat surfaces uniformly, but when they hit convex surfaces, it causes sound dispersion. Convex reflecting surfaces are lined on the ceilings and are used to disperse sound. Convex surfaces in section 30

31 Walls Tilted Walls The irregular walls of the auditorium are properly tilted to allow more useful reflecion of sound. These walls are lined and covered with fabric panels as well as hardwood. The hardwood surface allow the reflection of sound within the auditorium. Tilted walls in plan 31

32 Sound diffraction Sound diffraction occurs when the sound waves pass through an opening or around a barrier in their path, causing a change in direction. In the case of this auditorium, the balcony that houses the audio console became the obstruction that splits the sound waves that propagates from the speakers. The sound waves then pass through different directions, going to different floors of the auditorium. The cantilevered balcony is a narrow obstruction, giving the sound waves bigger wavelengths. 32

33 REVERBERATION TIME 33

34 On the basis of the presented results, we can see that the reverberation time is 0.6 seconds and is still within the exceeded normal RT of theater for speech, which is a maximum of 1 second. We have concluded that the reverberation time obtained is slightly shorter for the function of the room. Nevertheless it is still considered favorable because the paths of direct sounds waves to audience should be as short as possible, to reduce sound energy loss. Area (m 2 ) Absorption Coefficient Absorption Units Floor Carpet Parquet Wood Ceiling Gypsum Plaster Board Timber Hardwood Wall Left Fabric Panel Belian Timber Hardwood Gypsum Wall Board Right Fabric Panel Belian Timber Harwood Gypsum Wall Board Front Belian Timber Harwood Gypsum Wall Board Curtain Back Fabric Panel Belian Timber Harwood Glass Other 34

35 Cushioned Fabric Total Volume: m 3 35