1.0 INTRODUCTION In order to solve the problems associated with sound, there is a need to look at the acoustic component of the buildings. These include walls, furniture, windows, ceiling etc. sources of noise internal and external sources will also be looked into. The reason for these is because of the sensitivity of the organ of hearing. The ear which is the organ of hearing is very sensitive to sound and also has a range of decibel (db) it can bear. Once it is exposed to a range it cannot bear, there is bound to be Temporary Hearing loss (THL) or at higher ranges (e.g. 40dB) it could experience permanent a Hearing loss (PHL). To prevent such defects in hearing, approaches to reduce the noise level is considered. In large auditoriums, (theaters, cinema halls, or workshop halls etc), distortions of speech could be experienced due to acoustic and factors like echo, or reverberations. To bring about speech not allowing any form of interference, measures to overcome acoustic related factors is also considered. Acoustics being science of sound is an aspect or topic that cannot be overlooked in building. Poor insulation property exhibited by some of 1
the building components like windows, walls, ceilings, etc also increases the acoustic nature of the building. Therefore with the appraisal of any building, how the acoustic nature of a building can be improved, and the noise level, both internal and external can be reduced is what will be considered. 2
2.0 CHAPEL OF FAITH FUTA GENERAL DESCRIPTION Chapel of Faith is located at Obanla area of the campus behind the university sport center. Adjoining development/structure to this church building are: Saint Albert Catholic Church, Computer Resource Center, Continuous Education Center Lecture Theater, central borehole, university bookshop, and others. The landscapes of the premises are grasses and shrubs also trees are planted beside the Chapel. the building can easily be accessed by fairly good road networking. University library Chapel of Faith Computer Resource Center From Obakekere Saint Albert Catholic Church University Central Borehole Fig.1 Location map of the church under study 3
2.1 ACHITECTURAL DATA Chapel of Faith is a University Chapel built in some years back in Federal University of technology Akure. Like many others, basically the church is rectangular in shape with a gallery behind the Auditorium. The church auditorium is completed while the other part or phase is of the church is still under construction. The architectural detail of the auditorium can be best described on as follows. 2.1.1 CEILING FINISHES Polished timber ceiling board is used for the ceiling finishes. It was suspended with the aid of timber structure of 50mm by 50mm thickness at an interval of 1200mm by 1200mm. the ceiling board is tacked down to the timber structure with aid of timber joist of 25 mm by 50mm by 4
3600mm. The ceiling board is polished and decorated in different pattern. However, with the knowledge of basic acoustic and reverberation or echoes is usually caused by height of ceiling and more tends when the space is empty. 2.1.2 SITTING ARRANGEMENT The auditorium seats are plastic chairs. Except the seat at the alter for Chaplin and other reverends which are cushion chairs. The arrangement of the seats is of about thirty chairs per row and Eighteen chairs per column. As a matter of fact, all this plastic chairs are absorber of sound, and they contribute to the acoustic of the auditorium. 5
2.1.3 Walls Walls are usually the next most important surface. Their importance increases as a room decreases. Typically walls have very poor sound absorbing qualities. The kind of walls used for the church auditorium is the sandcrete block wall plastered with cement mortar. It is painted with cream texcote. Carpeting the walls or placing arc tiles/corkboard on the walls will increase sound absorption, absence reduction of sound level within the building. In some cases, installation of acoustic baffles is more convenient or spraying of treatment may be more economical. 6
2.1.4 FLOOR The floor of the church is furnished with terrazzo and the alter floor is covered with ceramic tiles. This can t do much as per noise reduction. Carpeting the floor will increase the NRC only to about 0.3 2.1.5 HEADROOM The Church Auditorium is made up of gallery at the back entrance. The headroom of the hall is about 6500m. This is a large room and this increases the reverberation time of the hall. 7
Therefore to reduce the reverberation of the hall, GSM material could be used as suspended ceilings which are a good absorbent material. Secondly the headroom could be lowered as to reduce the reverberation in the hall. 3.0 ACOUSTIC CONDITION OF THE BUILDING University Chapel is a large auditorium that is use for worship. It has a lot of elements that contributes to the acoustic condition of the building. This ranges from the noise generated externally to the internal ones. Looking at the location of the church, in front of it is a road linking senior staff quarter and the university central borehole. Therefore there is noise generated through traffic. Noise is also generated from the borehole. Other sources of external noise includes: noise from the generator of the Computer Resource Center, noise from the Catholic Church. Internal sources of noise include people or audience, church appliances; microphones, loudspeakers, drums, organs and others. In order to address the issue of acoustic control of the building, every element of the building components and design was carried out. 8
3.1 APPRAISAL OF ACOUSTIC SITUATION There are two main sources of noise to the building. These are the noise generated within the building and the noise from external sources. 3.1.1 INTERNALLY GENERATED NOISE The various sources of noise generated internally comes from the public address system, speakers, amplifier, voice (human), musical instrument, etc. 3.1.2 PATH OF TRANSMISSION This is through the sound borne structure element of the building i.e ceiling, walls, floor, and furniture. 3.1.3 REVERBERATION TIME 9
Reverberation is the persistence of sound after it has cease from its source. This is the consequence of reflection e.g. echo. Optimum reverberation of room depends on volume of space, type of room, total sound absorption and setting arrangement. Reverberation time is directly proportional to the volume t = 0.05V a Where t = reverberation time of the room V = volume of the room a = total room absorption From The headroom of the auditorium is about 6.5M. This enhance the reverberation time usually rise when the auditorium is totally empty. 3.1.4 BACKGROUND NOISE 10
The prevailing ambient noise from outdoor is from the traffic, generator of the Computer Resource Center, noise from the University borehole area. Another source of the background noise is the audience. 3.2 SOUND REFLECTOR This is enhanced by smooth surface of glass, walls, and window. 3.3 SURFACE MATERIAL The building material has a great importance on the acoustic situation. The element was carefully examined and detailed as follows. Ceiling made of polished timber ceiling board Floor made of terrazzo flooring and Ceramic Tile Wall it is made of sands Crete with glass window. 3.4 SEAT MATERIAL/LAYOUT The seat use in the church auditorium is single seat plastic chair. The arrangement of the seats is of about thirty chairs per row and eighteen chairs per column. 11
3.5 SOUND DIFFUSION AND DIFFUSERS Sound in an enclosure can be described as diffuse if the intensity of the sound energy is equal in every location of the room, or sound energy flows equally in every direction. Many different factors can enhance the diffused sound. These factors include geometrical irregularities absence of focusing surfaces, the distribution of absorptive and reflective elements randomly scattered through the space and the existence of diffusing objects (furniture). Therefore, in places like Chapel of Faith, sound is diffused due to the presence of wooden ceiling board. 3.6 SIZE AND SHAPE The building design is rectangular in shape with high headroom. The auditorium is about 37200m in length and16800m in breadth The size and the shape of the building allows for equal diffusion and distribution of sound. 12
4.0 IMPROVEMENT STRATEGY/REMEDY The acoustic condition of Chapel of Faith can be improved upon on, with the strategies or remedy as discussed below. 4.1 USE OF BARRIERS 13
Outdoor noise from traffic, people, and generator can be shielded with the use of rows of trees being planted to act as sound barrier, although acoustical effect is small. 4.2 ENCLOSURES The use of enclosures for the nearby generator of Computer Resource Center will suppress the noise from the generator. On the other hand, the internal lining of the auditorium with an acoustic absorbent also improves the acoustic condition of the church building. 4.3 COST AND THE DESIGNER During the design, the cost for the acoustic elements to be introduced into a building is usually high. Thus the acoustic designer is rarely allowed the luxury of a huge margin. 14
To acoustic consultants tasks is to achieve or strike a balance between a design that is too costly initially and for one far which failure will be disastrous. 4.4 FLOOR The upper surface typically is supported over a sub floor by an intervening soft layer that reduces the transmission of vibration into the main structure. To improve the insulation against impacts, it is necessary either to add a soft floor covering or resultantly support ceiling. The addition of a soft floor covering to a hard, heavy floor improves its impact insulation butt has a negligible effect on its airborne sound insulation. CEILING For the ceiling, the use of ceiling with collated/particle board are good sound absorber. Also, perforated current asbestos board is a good acoustic material as it is able to prove a rigid, durable, acoustically transparent feature. When sound waves strikes the surface of the material, a fraction of the 15
incident energy is absorbed by conversion heat. Acoustic materials are those materials whose primary function is to absorb sound. ACOUSTICAL TILES AND BOARDS An acoustical tile or board is an integral rigid, self supporting material furnished in prefabricated units of a definite size and thickness the distinction between acoustical board and tile is one of size only (boards are larger) the thickness range in general from 1.3cm to 3.9cm; ½in to 1½in. The many projects available in acoustic tiles or board form differ widely in composition and surface characteristics, with corresponding difference in properties other than sound absorption such as appearance, architectural style, clean-ability, paint-ability, high Reflectance, flame resistance and method of application. GLASS Sound insulation: it will be seen that the natural air leakages which occur around closed opening lights are very important. Sealed double glazing is therefore necessary for a superior level of insulation. The sound insulating advantages given by wider gaps can be further improved by the use of sound absorbent around the edges for windows. 16
SPECIAL GLASSES/PRODUCT (a) Laminated glass: - this is resistant to leakage, good as safety glass, varies from security laminated tough solar, sound, to fire resistance. (b) Double glazing: - this reduces thermal loss and condensation and provides sound insulation (c) Hollow glass block: - this is a fusion of two glass trays and used for non load bearing wall construction. It also has fire and sound resistance. WALLS Wall is an important component of the interior which has great effect of acoustic condition of the room. It has poor sound absorbing qualities. To improve the acoustic condition of the building, acoustic baffles should be used at the wall. The walls could also be treated with acoustic tiles. 4.5 SOUND CONTROL/INSULATION Sound insulation is the reduction of sound transmission of (air borne sound, impact sound) through wall floors and partition. This could be 17
achieved in the church building through appropriate sound insulation element with an adequate transmission coefficient. Sound reduction effect of element is measured in decibel (db). The recommended acoustic standard for auditorium or large hall like this is 30 40 decibel. Material to be used For this building, it is majorly used for worship, although, music goes alongside. The material to be used for the interior of the building with sound insulating properly must have the following characteristics 1. It must be soft 2. It must be fuzzy, that is soft light hairy texture. 3. It must be porous 4. It must be thick 4.6 BACKGROUND NOISE To establish good room acoustics, one should reduce background noises while preserving and reinforcing desired sounds. In achieving this, 18
reflecting surface should be chosen and placed for the purpose of directing and distributing sound throughout the room. Also, absorptive surfaces should be designated and place to presence of reflected sound that are no longer useful for reinforcement. PICTURE GALLERY 19
5.0 CONCLUSION Case studies are expedient in analytical studies and in the case of this report, the study of the acoustic conditions of the University Chapel of Faith has fortified the student with eclectic knowledge of acoustics, its successes and failure in buildings, noise sources and control and ways of apply it during design. With this study, it is interesting to note that in any enclosure or building, the noise level could be reduced to a tolerable level using appropriate acoustic measures. 20
Acoustic had made it possible for music to be going on in an auditorium and will not interfere with the peace of the city. There are materials that are design to absorb sounds, such that high range of sound that could damage the ear is reduced greatly. Noise can now be controlled and the issue of annoyance, disturbance, or irritation being prevented is another importance of acoustics. In large halls like cinema, theaters, auditorium, etc where reverberations, echoes, etc cannot be avoided with the use of acoustic baffles on the wall, Gypsum board at the ceiling, reverberations are eliminated and there is intelligibility of speech. Acoustics had been able to provide speech intelligibility or clarity unlike the case of distortion or interference in speechmaking which was peculiar to large auditoriums. The issue of acoustics being considered along side the building design is a great breakthrough and improvement in the building industry. It s still about considering the safety of man as we know that continuous exposure to high range of sounds is detrimental to the hearing of man. 21
6.0 RECOMMENDATION In the design of a building, designing with the acoustic aspect in mind, should be the practice of architects today. Just like we have schedules for windows, doors, paints etc, acoustic schedules should also be provided. The acoustic architect must ensure that the specifications are strictly adhering to. The study of acoustic has made us to see the importance of incorporating sound reduction measures to building resign. Unlike before, when the need or issue of noise is not seen as anything, the use of acoustic board like gypsum boards for the ceiling, spray-on treated or 22
acoustic baffles on walls of building, addition of carpets to the floor of buildings should be a normal practice in the construction of buildings. To also achieve maximum result, architecture we know has many branches, so there should be architects given to the study of acoustics who are veterans in this field. This will bring about acoustic consultants who can proffer solution to acoustic problems. It will bring about architects who know how to manage the issue of sound and noise alongside with the building construction. Enlightening people on the danger of continual exposure to sound and noise is also important. By this people are made to know that the issue of sound and noise is everybody s work. Everybody should be involved. Houses very close to roads or traffic area should use screen element like fence or having buffer zones to reduce noise from the main building. For the interior, the use of double glazed window which has a sound reduction of up to 42 45dB, closed single window has reduction of 20 25dB should be recommended for buildings. Putting all these treasures in place, it will go a long way in improving the safety of the building and in turn the health of man since sound deals with the organ of hearing the ear. 23
7.0 REFERENCES Microsoft Student 2008 [DVD]. Microsoft Corporation, 2006. Diamant, R.M.E. (1986): Thermal and acoustic insulation. University Press Cambridge. www.sdngnet.com 24