ARCHITECTURAL ACOUSTICS

Transcription

1 AN ASSESSMENT OF ARCHITECTURAL ACOUSTICS (A CASE STUDY OF SCHOOL OF SCIENCE BUILDING, FUTA) (ARC 507) CONDUCTED AND COMPILED BY ADARA RAWLINGS S. AYEGBUSI OLUTOBI G. LALEYE PELUMI ARC/03/1884 ARC/03/1913 ARC/01/9228 SUBMITTED TO THE DEPARTMENT OF ARCHITECTURE FEDERAL UNIVERSITY OF TECHONOLOGY, AKURE, ONDO STATE, NIGERIA. IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF BACHELOR OF TECHNOLOGY (B-TECH) DEGREE IN ARCHITECTURE APRIL, 2007

2 INTRODUCTION Architectural acoustics is the science of controlling sound within buildings. This is the science of controlling a room's surfaces based on sound absorbing and reflecting properties. Excessive reverberation time can lead to poor speech intelligibility, which can be calculated. Reflective surfaces can be angled and coordinated to provide good coverage of sound for a listener in a concert hall or music recital space. To illustrate this concept consider the difference between a modern large office meeting room or lecture theater with a traditional classroom with all hard surfaces. DESCRIPTION The building under study is the SCHOOL OF SCIENCE BUILDING at Obanla campus of Federal university of Technology, Akure. The building is located in the academic core of the institution and surrounded by structures. The adjacent structures include Schol of Agriculture building, Lecture Theatres, temporary Workshops, Stores, Offices blocks etc. and other natural and man-made features i.e. landscape, trees, shrubs, vegetation cover, kerbs, driveways, and walkways. The structure itself (School fo Science Building) consists of four wings connected together near the centre by courtyard, lobbies and staircases. The frontal wings are three floors each while the other rear wings are four floors each. Each wing on all floors has corridors linked to the central area of the structure. Also the wings at the ground floors has an exit at the end of the corridors. The element of the building are (i) Walls (ii) Vertical fins (iii) Concrete/steel balustrade (iv) Wooden window frame (v) Wooden panel door (vi) Louvred window blades (vii) Terrazo floor finish (viii) Concrete slab finished with cement screed (ix) Asbestos ceiling sheets etc. The structure accommodates and services a number of people, both students and lecturers, teaching and non-teaching staff. These people in one way or the other affect the acoustic properties of the structure due to the noise they generate. Other sources of noise are from the external that is the traffic/vehicular movement, pedestrian movement, wind load etc. FLOOR; The ground floors of the structure is a solid ground floor. It is a cement-sand screed on reinforced concrete slab finished with terrazzo. CEILING; The ceiling at the upper-most floor are made of asbestos ceiling sheet. The asbestos ceiling sheet are (1200x1200)mm each on 50x50mm noggins secured by battens and nails. At lower floors, slabs are used as ceilings. The slabs are supported at grids by beams at cross-sections. WALL; The walls are a combination of solid hollow sandcrete block walls and reinforced concrete wall. The lengths of the wall are further reinforced at interval by introduction of concrete walls and fins. The walls at some positions possess fenestrations for windows, door, archways etc.

3 SIZE, LOCATION AND PATTERN OF USE The laboratories are special classes designed to accommodate students for both their lectures and practicals. The worktops comprise storage spaces to keep their specimens, taps and wash-basins. The apparatus are being kept in the technologist office adjacent the laboratories. The laboratories are of various sizes. The biology laboratories are about m². The chemistry laboratories are within the ranges of m². Technologist offices are attached to these laboratories as mentioned above and these is a major design disadvantage because each time he moves in and out of the office he distracts the attentions of both the student and the lecturer. Activities that occur in the School of Science Building include: Lecturing, examination and practical and assessment of specimens in a light controlled environment Table top work, including educational works. Assessment of practicals and examinations carried out. Administration works in the offices, using a computer and printer practical hand washing using a hand wash basin with elbow action lever taps provided on the lab. Tables. Characteristics of the Space Speech intelligibility: The laboratories are made up of solid walls with windows and doors to offer good acoustic properties that prevent background noise from the lobby majorly. Doors are usually not locked during lectures to give room for the technologists to access their offices. Fenestration: The spaces have external windows and doors that are wide enough for very good ventilation and source of intrusion of noise from external spaces. Finishes: The floors of the building are finished with terrazzo, and the table top finished with ceramic tiles of 200x200mm dimension. The walls are finished with textcote paints Artificial lighting: The lighting fittings used are fluorescent tubes and incandescent bulbs to provide high levels of illumination. Special engineering services: None. Furniture, fittings and equipment: Furniture used include laboratories tables and stools for students. Fittings typically include a wash hand basin with water taps. Secure storage, shelving and rackage are provided for equipment and materials SITE PLAN SHOWING THE SOURCES OF NOISE Site Planning requires a considerable effort, bringing the quantitative and qualitative factors that will lead to transformation of the environment. It involves a systematic application of the complexities of the environmental conditions through a well conceived planning and decision process so as to enhance the lives of the occupants of the buildings and the environment in general.

4 The planning of an environment affects the functions and performance of the building. A properly planned environment and a properly designed building enhance the output of the users. The School of Science Building lacks both good designs and proper site planning. The design of the building is such in a way that noise is generated from all parts of the building. The design does not defines or separate public areas from semi-public areas. Offices, classrooms, laboratories, stairways, lobbies, corridors etc are haphazardly positioned on all floors. The environment of the building is also deficient. The car parks are a major source of noise which needs to be taken care of. The car is positioned too close to the building. Also noise generated from traffic/vehicular movements are not screened from the building. The orientation of the building in relation to the site is also a major aspect to be considered. This greatly affects the direction at which noise/sound wave is being transmitted into the building. Noise from temporary workshop Noise generated by movement of Noise from School of Agric. Science Building Noise generated by movement of Noise generated by vehicles at the car park Noise from adjacent structures Noise generated by movement of Noise generated by movement of EXISTING SITE PLAN SITE PLAN SHOWING SOURCES OF NOISE

5 A PORTION OF THE FLOOR PLAN SHOWING LABORATORY Office Office 1200x2700mm louvred window c Lab. table top finished with 200x200mm ceramic tile o r r 75mm thick reinforced concrete horizontal shading device Laboratory i d o r Terrazo floor finish on cement-sand screed 225mm hollow sancrete blockwall finished with brown textcote paint Office Office FLOOR PLAN SHOWING LAB. & OFFICES The floor plan of the structure is a four-wing structure. It has two at the rear and two at the front. The frontal wings have three floors each while the rear wings have four floors each. The ground floor of the frontal right wing of the section of the building is being taken for the study. The section combines a laboratory, offices and a corridor. The structure is a framed structure with hollow sandcrete blocks as the partitions. The walls possess fenestrations on both sides along the length of the walls. Entrances to the offices open directly into the laboratory hall. the users. The laboratory houses worktops with cabinets, wash-basins stools, writing board, tables, as well as All these have effects on the conditions of the building.

6 CEILING PLAN The section of the building under study is located on the ground floor and therefore makes use of the slab of the upper floor as its ceiling. the height of the ceiling from the floor is about 4m. the ceiling is a reinforced concrete lab with longitudinal and transverse beams at grids. The beams are 225mm wide and 300mm deep. O f f ic e O f f ic e 150m m rein forced concrete slab as c e ilin g 225x300m m rein forced concrete beam L abo rato ry W h ite e m u lsio n paint on sand-cem ent screed 225x300m m reinforced concrete beam O f f ic e O f f ic e C E I L I N G P L A N

7 PICTURE SHOWING THE FRONT ELEVATION OF THE SCHOOL OF SCIENCE BUILDING The front elevation of the building faces the southern part on the site. It is accessed by a considerable width of walkway flanked by edges to accommodate. The picture shows a vast space of parking space to accommodate vehicles. The parking space is position at the south-western area of the vicinity.

8 PICTURE SHOWING THE INTERIOR OF THE BUILDING These pictures depict the interior of the building. The users, equipment, structures etc. interact to affect and influence the acoustic conditions of the building. The instructor/lectures/technologist speak from the front of the laboratory where the board is positioned. The sound wave, before it reaches the end of the laboratory comes in contact with various obstructions which could posses one or more of the followings; reflective, absorptive, diffractive, refractive abilities. The sound waves at transmission strikes obstacles like wall surfaces, beams, window, doors, floors, tabletops, stool, chairs, ceilings, occupants etc. the sound waves are then reflected, absorbed, refracted, diffracted or further transmitted until it strike another surface. This continues in this manner until the energy in the particles of the sound waves is completely lost.

9 ANALYSIS OF SOURCES OF INTERNAL AND EXTERNAL NOISE First Floor Penetrated Noise Noise from vehicles SECTION THROUGH LAB. PICTURES SHOWING EXTERNAL NOISE SOURCES

10 Air-conditioners increase the noise level in the structure Noise generated by and their movement on the corridor. Noise is also generated from the mechanical actions of the pumping machines and also movement of water through he pipes PICTURES SHOWING INTERNAL NOISE SOURCES Noise generated by materials and equipment in contact such as the beakers, test tubes, conical flask, burette etc. Movement of the users on the floors also generates noise, which affects the acoustics of the building. Movement of the ceiling fans, fluorescing tubes noise, conversations by the users are also major sources of noise generated in the building.

11 GENERAL ASSESSMENT OF THE ACOUSTIC CHARACTERISTICS OF THE BUILDING Analysis Of Sources Of Internal Noise; Students murmuring during lecture. Noise from student s mobile phones. Noise from the technologist movement in and out of the office as earlier explained Noise from artificial lighting fittings. Noise from ceiling fans. Noise is generated from the baker, conical flask and other lab. Equipment as it touches the ceramic tiles on the tabletop. PICTURES SHOWING THE INTERIOR AND SOURCES OF INTERNAL NOISE

12 External noise sources; Noise from the pedestrian on walkways and the building corridors. Vehicular movement at the car park. Vibration from the pumping machine hangs on the external wall as shown in the picture below. Noise from the air condition machine. Noise from the blower placed on the service roof. GENERAL ASSESSMENT OF THE ENVIRONMENT There is the need for an overall assessment of the acoustic conditions of the general environment. As mentioned earlier, noise is an unwanted and a disturbance, which affects and reduces the productivity of the users. Noise has adverse effects on buildings, its functionality and as well reduces lifespan. Noise is generated at various sources and by several means in the environment. Users are to be protected from excessiveness of this. Noises generated by car engines of the vehicles at the parking spaces are transmitted directly into the classrooms, laboratories, and offices. This hence interferes with the activities of the occupants. Vibrations from the vehicles also gradually cause damage to the structure itself. Noise from mechanical devices and equipment on the wall of the building i.e. pumping machines, airconditioners etc. also directly generates noise which affect the acoustic conditions of the building. More importantly is the effect of noise on the occupants. Buildings are to be designed to enhance the quality of life of the occupants. Excessive exposure to these sources of noise can cause hearing damage, which may be temporary or permanent. Although all the spaces in the building under study are rectangular in shape with some of them with reasonable volume yet the effect of echo in these spaces is considerably insignificant and therefore negligible.

13 PROPOSAL FOR IMPROVING THE ACOUSTICS OF THE BUILDING BY AMELIORATING INTERNAL AND EXTERNAL NOISE. Looking at the spaces in the building. For instance the laboratories in the building, the major sources of internal noise to be dealt with include: Student s murmur during lecture. Noise from student s mobile phones. Noise from movement in and out of the laboratory.. Noise from materials and equipment. All these sources of noise may be difficult to eliminate completely but yet its effect can be reduced to the barest minimum by providing a loud speaker for the lecturer. Also the acoustic characteristics of laboratories must be improved upon by; Using high absorbing material on both the walls and the ceiling to bring the reverberation time of the incident sound to the acceptable level. Using soundproof windows and doors. Some of these acoustical panels that can be used are illustrated in the following drawing: Noise reduction coefficient NRC is the arithmetic average of the sound absorption coefficients at 250, 500, 1000, and 2000 Hz, then this average is rounded to the multiples of All these will not only ameliorate the internal noise alone but will also prevent the penetration of external noise into the interior. Other sources of noise coming from outside the building interfering with the activities going on in the building as can be seen in drawing below include; Noise from the pedestrian on walkways and the building corridors. Vehicular movement at the car park. Vibration from the pumping machine hangs on the external wall as shown in the picture below. Noise from the air condition machine. Noise from the blower placed on the service roof. Noise from the adjourning structures like the workshop adjacent to the building. Looking at the modified site plan shown below, larger percentage of the noise from the car park and those from walkways is being prevented from reaching the building with high intensity by planting shrubs along the noise path, while the remaining percentage is being taken care by acoustic material attached to the walls.

14 N oise from tem porary w orkshop N oise generated by m ovem ent of N oise from adjacent structures N oise from School of A gric. S cience B uilding N oise generated by m ovem ent of N oise generated by vehicles at the car park N oise generated by m ovem ent of N oise generated by m ovem ent of S IT E PL A N M IN IM IZ IN G Direction of Diffracted Noise Diffraction of Noise by Obstruction Penetrated Noise Noise absorbed and diffracted by landsape elements Direction of Diffracted Noise Noise from vehicles SECTION SHOWING REDUCED NOISE IMPACT PROPERLY LANDSCAPED BUILDING ENVIRONMENT ENHANCES ACOUSTIC QUALITIES OF THE ENVIRONMENT Noise generated by pumping machine can be handled in any of the following ways; Substitution of the noisy machine with a silent one. Complete removal of the machine from its present position to a distant place from the building, or The machine could be enclosed by sound-proof isolator either by single enclosure or by double partitions.

15 Echo In the case of introduction of a loud speaker to enhance audibility in any of these spaces the echo will definitely rise appreciably and hence this effect need to be taken care of to derive better acoustics property of the spaces. So, there are many tools available to the designer to eliminate echo. These tools include space layout, sound diffusing panels, absorption panels and electronic signal processing.