CBN FUTA COMPUTER RESOURCE CENTRE

Transcription

1 A WRITE UP ON ANALYSIS OF THE ACOUSTICS PROPERTIES OF CBN FUTA COMPUTER RESOURCE CENTRE BY OGANUFA J.C BAYODE O.O ROTIMI O.O ARC/01/9234 ARC/01/9215 ARC/01/9249 COURSE. ARC 507 ENVIRONMENTAL CONTROL III. (ACOUSTICS AND NOISE CONTROL) COURSE LECTURER. PROF. OLU OLA OGUNSOTE SUBMITTED TO THE DEPARTMENT OF ARCHITECTURE SCHOOL OF ENVIRONMENTAL TECHNOLOGY FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE IN PARTIAL FULLFILMENT OF THE REQUIREMENT FOR THE AWARD OF A BACHELOR OF TECHNOLOGY (B.TECH) IN ARCHITECTURE APRIL 2007

2 Pages TABLE OF CONTENTS 02 LIST OF PLATES 02 LIST OF FIGURES 02 INTRODUCTION 03 DESCRIPTION OF THE BUILDING 03 LOCATION 03 ARCHITECTURAL DESIGN 04 MATERIALS FOR CONSTRUCTION 04 NOISE SOURCES 09 FACTORS AFFECTING THE ACOUSTICS OF THE CBN FUTA CRC 12 A PERCEPTUAL ASSESSMENT OF THE ACOUSTIC CHARACTERISTICS 13 PROPOSAL FOR IMPROVING THE ACOUSTICS 14 CONCLUSION 15 REFERENCES 15 LIST OF PLATES Plate 1: The architectural design of the building. 04 Plate 2: The internal Wall finished with emulsion paint. 05 Plate 3: The asbestos ceiling Finish 05 Plate 4: The terrazzo floor Finish 05 Plate 5: The window type 05 Plate 6: The approach of the building 08 Plate 7: The building from the major road 08 Plate 8: The front elevation 08 Plate 9: The ceiling fan used in the building 09 Plate 10: The interior furniture of the building the computer room 09 Plate 11: Centre for Continuing Education the Source of outdoor noises. 10 Plate 12: The car park a Source of outdoor noises 10 Plate 13: The generator a Source of outdoor noises 10 Plate 14: The access road Source of outdoor noises 10 LIST OF FIGURES The plan of the floor of the building showing furniture and floor finish 06 Ceiling plan of the building 07 The site plan showing sources of noise 11 2

3 INTRODUCTION Architectural acoustics is primarily aimed at enhancing speech and music clarity in enclosed spaces. Due to hearing complications arising from both the physiological and psychological peculiarities of individuals, it is necessary to incorporate environmental control factors like acoustics in building designs. This is most effective when done in the early stage of design as opposed to the postconstruction phase, which is most prevalent today. Architectural acoustics entails room and auditorium acoustics. Reverberations due to reflections from walls and furniture influence room acoustics; for this reason, a broadcasting studio should have a normal degree of reverberation to ensure natural reproduction of sound. For best acoustic qualities, rooms are designed to produce sufficient reflections for naturalness, without introducing excessive reverberation at any frequency, without echoing certain frequencies unnaturally, and without producing undesirable interference effects or distortion. A failure to adhere to these principles of architectural acoustics leads to the generation of unwanted or damaging sound that will adversely affect the activities of intended users when the space is in use. This report is a study of CENTRAL BANK OF NIGERIA COMPUTER RESOURCE BUILIDNG, located in the Federal University of Technology Akure. It aims at examining the building s acoustics conditions with a lucid explanation of the effect of building s size, its characteristic shape, and use of materials in effectively enhancing speech clarity and combating noise problems in order to ensure satisfaction for the users. In addition, noise problems, that where not sufficiently dealt with in the design stage and others that have arisen over the years of occupation will be identified and solutions to alleviate them will be proffered. DESCRIPTION OF THE BUILDING The CBN-FUTA Computer Resource Centre is one of the institutional buildings located in the Federal University of Technology Akure campus. It is a centre for multifarious activities, which includes; Lectures, Internet browsing, dining, conferencing, etc. This heterogeneity of activities constitutes a major acoustic problem as the acoustic conditions for each space differs considerably. The methodology employed in combating this problem will be examined, further on in this paper. LOCATION The CBN FUTA Computer Resource Centre is located at the Obanla campus of the Federal University of Technology Akure The building is bounded by the Library Complex to the West, Center for Continuing Education (CCE building) to the East, Computer Resource Center phase II to the Northwest, Water-Works to the North and parking lots to the Northeast. 3

4 ARCHITECTURAL DESIGN The design is an architectural masterpiece designed by Professor Olu Ola Ogunsote, a lecturer in the Department of Architecture in the School. Completed in March 2003, the building is designed to cater for the increasing need for information technology level of the school (both students and staff). It has a fascinating form achieved from a peculiar combination of polygonal shapes in a decreasing and astonishing manner. It comprises of three computer rooms, a lecture / conference room, a coffee room, a workshop, the administrative offices and conveniences. A polygonal-shaped courtyard is also incorporated into the design to assist in the provision of both natural ventilation and lighting. Its strategic location provides a central access to both the students and the staffs from the lecture hall and offices thus, buttressing its definition as a supporting facility. In addition, there is a remarkable landscape design, thereby creating an eye-catching environment, which is always pleasing and conducive for learning. Apart from the aesthetic value of the landscaping elements used, the issue of micro-climatic modification cannot but be mentioned as it is a paramount tool for ensuring a building s adaptability to the harsh climatic conditions of the environment. Plate 1: The architectural design of the building The use of vertical elements such as fins and parapet walls, and exaggerated horizontal elements such as the wide corridors in the design also helps in the building s adaptability to the environment as they keep the building in shade even when the sun is directly overhead. The parapet walls are very characteristic as it is very low (in relation to the windows) and at the same time, very high (in relation to the roof). A simple eccentric mono-pitch caps the low building. However, the roof is so low that it is hidden well from view by the parapet wall. MATERIALS FOR CONSTRUCTION The construction materials used for the various components are as follows WALLS 225mm X 225mm X450mm sandcrete block walls were used in the construction of this building, and they were rendered externally with texcote paint and internally with emulsion paint. In wet areas such as toilets, decorative ceramic glazed tiles were used as wall finish from the floor to the door height. Gloss paint 4

5 was then used to complete the remaining surface area. Texcote paint was also used to finish the rendered concrete columns and fins. Plate 2: the internal Wall finished with emulsion paint. For skirting, mahogany with decorative profile was used in the director s office, ceramic tiles skirting is used in the toilets, while pre-cast terrazzo tiles skirting was used in the computer rooms, lecture room, coffee room and at the corridors/lobbies. CEILINGS The ceiling is made of 1200x1200mm asbestos ceiling boards painted with white emulsion paint and has a flat shape, which runs through the building ceiling. Plate 3: the asbestos ceiling Finish FLOOR All floors were finished with in-situ terrazzo, except for the toilets, where nonslippery ceramic tiles were used. PVC tiles was used in the director s office and carpeted with a non-patterned rug. Plate 4: the terrazzo floor Finish FENESTRATIONS All doors are timber-paneled doors, except the entrance and exit doors, which are iron grill doors. Window openings are made of glass pivoted sash with aluminum frame. Plate 5: the window type 5

6 THE PLAN OF THE FLOOR OF THE BUILDING SHOWING FURNITURE, MATERIALS AND FLOOR FINISH. director commitee room 2 secretary staff room work shop female toilet male toilet open courtyard computer room 3 photo copy commitee room 1 computer room 2 coffee room KEY DESCRIPTION PVC TILES TERRAZO RUG lecture / conference room computer room 1 FLOOR PLAN SHOWING FURNITURE ARRANGEMENT AND FLOOR FINISH 6

7 CEILING PLAN OF THE BUILDING work shop director commitee room 2 secretary female toilet male toilet computer room 3 commitee room 1 staff room lecture / conference room open courtyard computer room 2 photo copy coffee room computer room 1 7

8 Plate 6: the approach of the building Plate 7: the building from the major road Plate 8: the front elevation 8

9 NOISE SOURCES IN CBN FUTA COMPUTER RESOURCE CENTRE Noise is usually defined as unwanted or damaging sound. Numerous ways exist by which noise interferes with the activities going on in the building. These can be discussed under two major headings: Indoor noise. Outdoor noise. SOURCES OF INDOOR NOISES The primary source of indoor noise is the verbal interaction between the users in the building. In as much as architectural acoustics aims at speech intelligibility, a space such as the CBN-FUTA, which is a conglomeration of various activities, generates so much patterns of speech at differing frequencies and amplitudes that if unregulated, amounts to a noise problem. This level of noise only succeeds in creating interference in verbal communication as one verbal communication may be affected by the other and vice versa. This is further compounded by their proximity. In addition, electrical appliances like ceiling fans, air-conditioning and computer systems constitutes a noise problem in the building. The engines and rotating blades (especially in faulty fans) of ceiling fans and air conditions and the fans and clanking of the keyboard are some of the ways through which these electrical appliances generate noise. It is pertinent to note that the level of noise generated by these appliances is disturbing or annoying. Plate 9: the ceiling fan used in the building Plate 10: the interior furniture of the building the computer room Other sources of indoor noise include footsteps, movement of furniture on the hard terrazzo floor, banging of doors, etc. These are categorized as impact sounds which at very high levels may cause hearing damage. 9

10 SOURCES OF OUTDOOR NOISES The CBN-FUTA is bounded on the east by Centre for Continuing Education (CCE lecture hall) and its sister facility, the CCE Office complex. The CCE lecture hall is an auditorium used for lectures, seminars and conferences. This thus poses as a major source of background noise to the CBN FUTA building where required noise levels are very low. Plate 11: CCE building; a source of outdoor noises These three buildings, the CBN- FUTA, the CCE lecture hall and the CCE Office complex all share a parking lot which is sited behind the CCE lecture hall and extends beyond it to the CCE office complex. A very large volume of traffic thus employs this service and this goes a long way to compound the noise problems generated from this area. Plate 12: The car park; a source of outdoor noises Furthermore, the humming sound produced by the Mikano generator, which services the building in the event of power outage, constitutes a source of background noise. The generator is located behind the building in a shed. Its noise emission value is high and increasingly annoying and in effect, constitutes another source of background noise. Plate 13: Generator; a source of outdoor noises Finally, vehicular activities from the flanking access road at the front of the building also serve as a source of outdoor noise to the CBN-FUTA building. These activities could be in the form of engine noise, hooting of horns, etc. Plate 14: the access road Source of outdoor noise 10

11 female toilet male toilet -Acoustics analysis of CBN FUTA Computer Resource Centre- THE SITE PLAN SHOWING SOURCES OF NOISE CAR PARK COMPUTER RESOURCE CENTER PHASE 2 SATELLITE DISH GENERATOR NOISE PRODUCED FROM THE work shop HUMMING GENERATOR. commitee room 2 director staff room secretary lecture / conference room open courtyard computer room 3 photo copy commitee room 1 computer room 2 coffee room NOISE PRODUCED FROM THE CAR PARK NOISE PRODUCED FROM CENTRE FOR CONTINUNG EDUCATION. CENTRE FOR CONTINUNG EDUCATION computer room 1 NOISE PRODUCED FROM THE MAJOR ROAD. NORTH TO STAFF QUARTER. OBANLA - OBAKEKERE ROAD. CAR PARK FUTA LIBRARY SCHOOL OF ENGINEERING AND ENGINEERING TECHNOLOGY SITE PLAN 11

12 FACTORS AFFECTING THE ACOUSTICS OF THE CBN FUTA COMPUTER RESOURCE CENTRE The factors that affect acoustics of a busy institutional building such as the CBN FUTA Computer Resource Centre include its size, shape nature of materials and finishes, zoning etc. In attempting to analyse the acoustic performance of a building all these must be considered. SIZE AND SHAPE These greatly affect acoustic condition in a room and are the reasons for the definition of any acoustic condition. The reverberation time increases with the size of a room and depending on the size, the reverberation time could rise above acceptable standard. In the CBN-FUTA Computer Resource Centre, the hexagonal shape and size of the spaces in the building define an excellent acoustic characteristic. Compared to the conventional rectangular shapes of rooms, the characteristic shape of the spaces in the CBN-FUTA Computer Resource Centre enhances the acoustic condition. The size of the spaces which are not as large as that of an auditorium makes the need for resolution of acoustic problems minimal due to the fact that the problems are in fact, of a minimal nature. However, the 6-sided nature of the walls constitutes a high surface reflectivity, but this is of low importance in most of the spaces due to their reduced area. In any case, special acoustic treatment should have be given to areas such as the conference rooms, which requires a high speech intelligibility. FINISHES The finishes used in the building can greatly affect its acoustic properties; thus, it is advisable to use sound absorbent materials as finishes. In the CBN- FUTA Computer Resource Centre, the choice of terrazzo as the floor finish poses an acoustic problem due to its hard, reflective surface as it increases the reverberation effect in the room. This does not favour the acoustic characteristic in the space, but an alteration such as the introduction of rug like in the director s office could help to increase the acoustic nature. The wall finish used in the building is emulsion paint on rendered block wall. The block wall has a poor acoustic property. Cement plaster has a low absorption coefficient, 0.03 at 1000Hz. A soft porous covering is sometimes used to aid absorption. Asbestos ceiling sheets was used as the ceiling finish in all part of the building. This is not a positively inclined acoustic material due to its hard and smooth surface. However, due to the small-sized nature of the spaces in this building, the acoustic importance of the ceiling is less important as compared with other finishes in the rooms. It can be deduced from these points above that the major finishes used in the CBN-FUTA Computer Resource Centre does not help to attain an excellent acoustic performance, but the design which is the first point of solution to any acoustics space helped in alleviating the noise problems to a large extent. 12

13 ZONING Zoning is seen as a vital aspect of acoustics conditions in a space as it helps to check the predictable problem of noise at the design stage. In the CBN-FUTA Computer Resource Centre, proper zoning of the spaces was put into consideration, the differing activities in the building were put together in a manner to segregate the more noisy area from the quiet area, for instance, the entrance foyer, conference room and the computer rooms, which are noisy areas are properly zoned away from spaces like the director s office, and secretary s office, which on the other hand, are quiet areas. A PERCEPTUAL ASSESSMENT OF THE ACOUSTIC CHARACTERISTICS OF THE MAIN HALL IN THE CBN FUTA COMPUTER RESOURCE CENTRE WITH BACKGROUND NOISE, REVERBERATION AND ECHO The acoustic characteristics of the main hall in the light of background noise, Reverberation and echoes are discussed below. BACKGROUND NOISE The CBN-FUTA Computer Resource Centre was provided with most of the necessary acoustic components from its design stage through construction to its occupation. This was achieved using design procedures rather than the use of construction materials and in any case, sufficiently helped to reduce background noise to the barest minimum. More still, background noise from activities of students around and adjoining facility as well as vehicular noise are properly shielded from the building. REVERBERATION Highly reflective materials, such as a concrete or tile floor, brick walls, and windows, will increase the reverberation. Absorptive materials, such as curtains, heavy carpet, and people, reduce the reverberation. Bigger rooms tend to have longer reverberation times. On the contrary, reverberation in the CBN-FUTA Computer Resource Centre is relatively minute and unnoticeable due to the smallsized nature of the rooms. ECHO The spaces in the CBN-FUTA Computer Resource Centre are not too large, hence echoes are not really pronounced. The only probable spaces where this might constitute a problem are the large computer room and the lecture room. These spaces however, do not experience this distinct repetition of sound due to the absorbent nature of the upholstery in the halls, the absorbent nature of the ceilings, etc. The terrazzo floor finish and the non-carpeted walls, manysided walls and the fenestrations however pose a problem as they increase the reflectivity of sound in the space, thus aiding echo. 13

14 PROPOSAL FOR IMPROVING THE ACOUSTICS OF THE CBN FUTA COMPUTER RESOURCE CENTRE The approaches to the improvement of the acoustic environment of the building can be highlighted under the two categories of noise sources i.e. outdoor and indoor noise. These suggested approaches are proffered in a bid to reduce noise levels to tolerable or barest minimum levels. PROPOSAL FOR REDUCTION OF INDOOR NOISE The following are proposed ways in which indoor noise can be further reduced in the CBN-FUTA building. INSTALLATION OF CARPET ON THE FLOOR It is widely known that impact noise such as furniture movement, banging of doors and footsteps are less in carpeted rooms as compared to rooms with hard floor finish. Carpeting the floor reduces the Noise Reduction Co-efficient (NRC), thus ameliorating the effect of impact sounds. Carpets however have high maintenance costs, but this high cost could be balanced with the acoustic benefits of sound absorbance. USE OF ABSORBENT SCREENS AND SURFACES Absorbent materials and surfaces are efficient in reducing noise ensuing from air borne sound such as human voices as well as any other internally generated noise that would have been aggravated by multiple reflections from surfaces. The following available types of sound absorbers could be used: Porous absorbents Membrane absorbents Resonant absorbers Perforated panel absorbents. USE OF A SOUND REINFORCEMENT SYSTEM This consists of a wireless microphone used by the speaker to pick up his voice; the voice is then amplified and played through a loudspeakers srategically located in the hall to increase the loudness of the speech sounds for the listeners in the hall, thus preventing the speaker from shouting in order to make himself / herself audible. REDUCING THE SIGNAL STRENGHT AND INCREASING NOISE LEVEL Use of absorptive material reduces the signal strength and the increment of noise level. For instance, in the computer room, playing of soft music could helps to increase speech privacy and concentration within the spaces. PROPOSAL FOR REDUCTION OF OUTDOOR NOISE Suggested ways for further reduction of outdoor noise in the CBN-FUTA building are: 14

15 SCREENING In the CBN-FUTA Computer Resource Centre situation, the noise coming from the center of continuing education can be screened off using a fence or a buffer zone such as trees to aid acoustic serenity. INSULATION This can be useful in reducing the noise coming from the road. An insulating material can be embedded between the existing wall facing the road directly and a new one to be constructed directly behind it; the resulting insulated double skin wall offers a greater insulation from traffic noise. To make this approach more workable, the front door will have to be permanently closed or better still, changed to a double glazed aluminum framed door provided with door closers to ensure that it is closed after each use to disallow noise infiltration. ISOLATION The noise from the Mikano generator behind the building can be reduced by isolating the generator completely. For example, the use of effective silencers and employing the buy quiet method. CONCLUSION. Controlling noise is a subject, which should be given prime consideration in any academic and administrative environment; most aspects of learning require a serene environment to aid the concentration of the users. Aside the spatial requirements, other factors such as construction materials, site zoning, and design are equally significant and these should be sufficiently incorporated in the design process to assist in the resolution of acoustic problems. Finally, an acoustic consultant should be included in both new and remodeled learning facilities to aid a suitable learning environment. In a bid to reduce construction cost, this aspect of the design is often neglected, and more often than not, it proves to be detrimental in the end because acoustic problems are generated at a later phase. In treating these problems, much more than would have been necessary (if it had been addressed at an early stage by a consultant) is spent. REFERENCES. Professor Olu OlaOgunsote. Acoustics and Noise Control Lecture notes Gary W Seiben, Martin A. Gold, Glenn W Seiben, Michael G. Ermann. (2000); Language Speech and Hearing Services in Schools. Vol.31. pp Ivor H. Seeley,(1974); Building Technology, sound insulation pp