A
WRITE – UP
ON
ACOUSTIC PROPERTIES
OF
BUILDING MATERIALS COMMONLY USED FOR CONSTRUCTION OF HOUSES IN NIGERIA
COMPILED BY
AKINSIPE AYOOLA
(ARC/09/7356)
GROUPA-8
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF BACHELOR OF TECHNOLOGY IN ARCHITECTURE
TO
THE DEPARTMENT OF ARCHITECTURE
SCHOOL OF ENVIRONMENTAL TECHNOLOGY
FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE
Lecturer: Prof. Olu Ola Ogunsote
Arc. Ganiyu
JULY, 2014
TABLE OF CONTENT pages
ABSRACT…………………………………………………………………………………...iii
1.0 INTRODUCTION………………………………………………………………………. 1
2.0 BUILDING ACOUSTICS AND MATERIALS………………………………………. 2
3.0 ACOUSTIC PROPERTIES OF SPECIFIC BUILDING MATERIALS…………… 4
3.1 Sound absorptive properties of materials…………………………………….. 4
3.2 Sound reflective properties or transmission loss of materials……………… 11
4.0 CONCLUSION …………………………………………………………………………15
5.0 RECOMMENDATIONS……………………………………………………………….15
6.0 REFERENCES………………………………………………………………………….15
ABSTRACT
Acoustics in a higher citadel of learning, as a matter of fact as a course under the department of architecture is a necessity.
This came to life with the need for students to understand the acoustics of spaces both interior and exterior, as well as to be able to design acoustically functional spaces that will enhance the intelligibility of sound or speech.
In addition to this, there is a rapid increase in loss of hearing caused by agents of hearing damage such as threshold shifts, sociocusis, due to an uncontrolled means of sound propagation. Hence, the need for the study of acoustics and infact the materials used to enhance it.
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1.0INTRODUCTION
What is acoustics?
Acoustics is a term sometimes used for the science of sound in general. It is more commonly used for the special branch of that science, architectural acoustics, which deals with the construction of enclosed areas so as to enhance the hearing of speech or music.
It could as well be regarded as the branch of architecture that deals with the control of sound which showcases the reflective, absorptive properties of sound.
Acoustics is a subject that describes all aspects of sound and falls into the fields of both science and art. The science of sound envelops the technicalities of its generation, propagation and reception as well as objectively describing its qualities. In the artistic world, sound plays a large part in terms of the spoken word, music and other auditory experiences that give us pleasure.
In most cases, the acoustics of a room will be satisfactory if a proper balance between sound-absorbing and sound-reflecting materials is created. In achieving this, reverberation as a factor should be taken into consideration.
For modifying the reverberations, the architect has two types of materials, sound-absorbent and sound-reflecting, to coat the surfaces of ceilings, walls, and floors. Soft materials such as cork and felt absorb most of the sound that strikes them, although they may reflect some of the low-frequency sounds. Hard materials such as stone and metals reflect most of the sound that strikes them. The acoustics of a large auditorium may be very different when it is full from when it is empty; empty seats reflect sound, whereas an audience absorbs sound.
Hence, a study of the acoustic properties of various building materials in order to broaden the scope of the students of architecture and to facilitate the selection of quality materials that will ensure good acoustics all round a space is needed.
It should however be noted that there are various materials used to achieve a good acoustic in construction, but for the purpose of this analysis, few number of materials will be mentioned.
Aims and objectives
The study of the acoustic properties of various building materials is to achieve the following objective;
1. To ascertain precisely, the type of material that will be used to achieve a particular sound level within a space.
2. To broaden the scope of the student in the field of acoustics.
3. To help in determining the various uses of different materials.
4. To be able to analyze the acoustics of buildings.
5. To know the wide varieties of materials that is available for the said purpose.
6. To be able to solve the problem of acoustics within an interior space as well as the exterior space.
2.0 BUILDING ACOUSTICS AND MATERIALS
Noise control as the name suggests, envelops the techniques used to minimize the effects of unwanted sound and thus optimize environmental conditions. In the construction industry, Building Acoustics is the term which covers this aspect of sound. Building Acoustics involves both the control of noise within an enclosed space and the reduction of noise between rooms or from either outside or inside a building.
Building Material is any one of various substances out of which buildings are constructed. They come in different forms and are also applied in various ways in building. Materials in building construction for the purpose of this write-up will be classified under the four major component parts of a building. This includes the following;
1. Walls
2. Floors
3. Ceilings
4. Roofs
Components of Building And Their Materials
1. WALLS: This is regarded as flat side of building or room, a vertical structure forming an inside partition or an outside surface of a building. It can as well be seen as a standing structure that surrounds or blocks, a narrow upright structure, usually built of stone, wood, plaster, or brick, which acts as a boundary or keeps something in or out. Other materials used in wall construction include,
▪ Glass (as curtain walls), ▪ Sandcrete blocks, ▪ Plastics, ▪ Tiles (mosaic)
2. FLOORS: It is a part of room to walk on: the flat horizontal part of a room on which people walk. The material used in construction include;▪ Timber or wood, ▪ Concrete, ▪ Tiles, ▪ Stones
3. CEILINGS: It is seen as the inside top of room: the overhead surface of a room, or the material used to line this surface. The overhead surface of a room, opposite the floor. Usually the term refers to a flat, beamed, or curved surface that conceals the underside of the roof or the floor above, but it may also refer generally to the exposed underside. There are several materials used for this purpose and they include,
▪ Asbestos ceiling boards, ▪ Celotex boards,
▪ Timber panels, ▪ Plaster of Paris (P.O.P)
▪ Acoustic boards
3. ROOFS: It is the upper covering of building: the outside covering of the top of a building, or the framework supporting this. They are made of materials such as.
▪ Plastics (acrylics), ▪ Aluminium Sheets, ▪ Clay tiles, ▪ Asbestos
3.0 ACOUSTIC PROPERTIES OF SPECIFIC BUILDING MATERIALS
It is very important to distinguish between sound absorption and sound transmission loss. Sound absorbing materials control sound within spaces and function by allowing sound to pass through them relatively easily. They are generally porous and absorb sound as a result of many interactions. Conversely, a material or system, that provides a good sound transmission loss is usually non-porous and a good reflector of sound.
3.1 SOUND ABSORPTIVE PROPERTIES OF MATERIALS
Noise is generally controlled within a space using sound absorbing materials. Sound absorption relates to the percentage that effectively disappears when the sound wave hits a body or surface. Sound absorption is evaluated by measuring the reverberation time of a room. The reverberation time is defined as the time taken for the noise (sound pressure level) to fall to 60dB below its original level when a sound source ceases to operate. If the reverberation time is long then the room will be live and the conditions will be acoustically uncomfortable for most activities. If the reverberation time is too short then sounds such as music may appear flat and lack character
Assuming that the material has greater sound absorption than the room surface on which it is installed, the reverberation times which are again measured will now be shorter than in the empty condition. A hard concrete surface has a very low sound absorption coefficient (less than 0.05 at most frequencies), whereas a thick carpet and underlay can approach 1. Acoustic consultants use the absorption coefficients of materials to estimate the reverberation times of specific buildings. However, in many rooms for example small offices, it is sufficient to specify totally covering one or two surfaces with a good sound absorbing product such as carpet or a mineral fibre tile ceiling.
The following building materials have good sound absorbing qualities;
● Acoustical Ceiling Tiles Characteristic features
• No Fiberglass-Non-Fibrous • Moisture Resistant-Indoor-Outdoor • Impact Resistant • Light Weight Ceiling Tiles
●Description of Acoustical Ceiling Tiles
MATERIAL: Semi Rigid Porous Expanded Polypropylene Acoustical Bead Foam (P.E.P.P.). PATTERN: Non Abrasive, Slightly Textured, Porous FEATURES: Lightweight, Impact Resistant, Moisture, Bacteria & Fungi Resistant, Tackable Surface APPLICATIONS: Gymnasiums, Auditoriums, Classrooms, Swimming Pools, Ice Arenas, Clean Rooms, Food Processing Plants, Food Prep Areas, Cafeterias & Restaurants, Manufacturing Plants, Car Washes, Rooftop and Machine Enclosures, Gun Ranges, Dog Kennels, Locker Rooms. THICKNESS: 1” & 2” SIZES: Nominal 2’x2’, 2’x4’; Custom Sizes Available COLOR: White, Charcoal FLAMMABILITY: ASTM E84, Class A. 1": Flame Spread: 3, Smoke
Developed: 84. 2”: FlameSpread: 5, Smoke Developed: 11 3 INSTALLATION: Glue up direct or as a lay-in tile in a suspended t-bar grid system. WEIGHT: 1" = .25lbs/Sq ft 2" = .45lbs/Sq ft
Graph showing absorption coefficient in relation to their frequencies
Sound silencer-sound transmission loss(STC)
125Hz / 250Hz / 500Hz / 1Hz / 2.5Hz / 5Hz / STC1" / 6 / 5 / 7 / 8 / 10 / 15 / 9
2" / 9 / 8 / 10 / 10 / 17 / 22 / 13
1" w/5/8" Gypsum both sides / 27 / 27 / 29 / 31 / 32 / 45 / 32
Table showing the Sound transmission loss of acoustic ceiling tiles
● Noise S.T.O.P Acousti-Board
Characteristic features
▪ Sound Deadening
▪ Sound Absorbing
▪ Insulating
▪ Low Cost
● Description of Noise S.T.O.P Acousti-board
MATERIAL: Recycled Wood Fiber Residue. PANEL SIZE: 2' x 4' or 4'x 8' THICKNESS: 1/2" DENSITY: 15 to 20 lbs. Per Cubic Foot. WEIGHT: .65 lbs./sq. ft. INSULATING VALUE: R=1.22 at 1/2" (ASTM C518) NRC: .35 (ASTM C423) STC: 26 (ASTM E-90)
APPLICATIONS: Acoustical-Board can be used as a Flooring Underlayment or as a Damping Layer between Studs and Gypsum Board to Improve Sound Transmission Class (STC) of Gypsum Drywall Partitions. Schools, Apartments Buildings, Townhouses, Condominiums. Noise S.T.O.P. Acoustical-Board™ meets the Requirements of ASTM-C 208, the Specification for Cellulosic Fiber Insulating Board.
CAUTION: Noise S.T.O.P. Acoustic-Board is Combustible and May Smolder if Ignited. Do Not Expose to Flame or Prolonged Excessive Heat Above 212¡ F without Sufficient Thermal Protection or Use Between Layers of Noncombustible Material. Specifications for Cellulosic Fiber.
● Foam S.T.O.P Pyramid (Melamine Foam Sound Absorber)
Characteristic features
• High Performance Absorber
• Increased Absorptive Surface Area
• Fiber Free • Class A Fire Retardant
● Description of Melamine Foam Sound Absorber
MATERIAL: Open Cell Melamine Acoustical Foam PATTERN: Pyramid for Monolithic Appearance FEATURES: Increased Surface Area, High Performance, Light Weight, Dramatic Visual Effect APPLICATIONS: Ceilings, Walls, Industrial, Commercial & Home Audio Markets, Broadcasting and Recording Studios
THICKNESS: 2”, 3 ”, 4 ” and Custom SIZES: 2’x2’, 2 ’x4’ (Custom Sizes Available) DENSITY: 0.7lbs/cub. ft. COLORS: Natural White, Latex or Cleanable DuPont Hypalon Paint - Black, Light Grey, Almond, White (Custom Colors Also Available)
FLAMMABILITY: ASTM E84, Class 1. Flame Spread: 5; Smoke Developed: 50
INSTALLATION: ASI S.T.O.P Noise Acoustical Adhesive
FOAM STOP: Sound Absorption / Noise Reduction per ASTM C423-90a125Hz 250Hz 500Hz 1KHz 2KHz 4KHz NRC
2” 0.07 0.25 0.60 0.94 0.97 1.08 0.70
3” 0.18 0.44 0.96 1.14 1.18 1.19 0.95
4” 0.16 0.62 1.10 1.20 1.21 1.22 1.05
Table showing Sound absorption/ noise reduction of melamine foam sound absorber
●Absorptive/Noise Barrier Quilted Curtains
Characteristic features
• Equipment Enclosures • Cost Effective Room Dividers • Water & Chemical Resistant • Exterior Applications
● Description of Absorptive/Noise Barrier Quilted Curtains
MATERIAL: Melamine Foam or fiberglass core, faced with quilted aluminized fabric. Optional Noise Barrier Septum.
PATTERN: Quilted Diamond Pattern FEATURES: Effective and durable sound absorber with mass loaded vinyl barrier option. APPLICATIONS: Used as an economical, effective noise barrier and sound absorber to enclose many types of noise sources or work areas. The curtains can be custom fabricated to almost any application. Can be used in exterior applications, waste water treatment facilities, industrial, commercial & residential applications. THICKNESS: 1”, 2”, 3", 4" SIZES: 48” & .54” Wide; Lengths up to 25’ (Custom Sizes Available) COLOR: Silver (Other colors available upon request) FLAMMABILITY: ASTM E84, Class A. Flame Spread: 23; Smoke Developed: 30
INSTALLATION: Hook and loop fasteners, grommet hangers, curtain spanport hardware. CURTAIN S.T.O.P.: Sound Transmission Loss - ASTM E90Frequency 125Hz 250Hz 500Hz1KHz2KHz4KHzSTC
1” Thick w/ Barrier 11 16 24 30 35 35 27
2” Thick w/ Barrier 13 20 29 40 50 55 32
3.2 SOUND REFLECTIVE PROPERTIES OR TRANSMISSION LOSS OF MATERIALS
Sound is enhanced within a space through the use of reflectors and diffusers. Sound absorption relates to the percentage that effectively disappears when the sound wave hits a body or surface. Transmission loss (TL) is the loss in sound power that results when sound travels through a partition. The more power that is lost, the greater the TL. The figure below shows the sound transmission loss in different building materials. Sound absorption is evaluated by measuring also the reverberation time of a room. Therefore where possible, we design a space to have an optimum reverberation time for its use.
Sound transmission loss through building materials
In construction, different building materials are used for the purpose of acoustics and these materials vary according to their location and are also based on the amount of sound required in the space. Also, the idea of curved surfaces is imbibed in a way to enhance the reflective properties of the room.
The following materials have good reflective properties necessary to enhance a good acoustics within and outside a space;
●Silent Screen Panels
Silent Screen absorption panels are designed to provide both sound absorption and sound transmission loss. Tpanels consist of individual sections, each 12 inches wide, mounted horizontally on top of one another, or vertically, side by side. Each section consists of a 2 3/4 inch deep, 16 to 22-gauge tray. Typically, the tray is
filled with six-pound density mineral wool, and covered with a perforated 22-gauge face panel.
● VISTA Panels
When some degree of visibility is required for safety or monitoring purposes, EAS Acoustical Panels can incorporate a high strength Lexan-type material which has a clarity rivaling glass, but is much stronger. VISTA panels also are abrasion and ultraviolet resistant.
VISTA panels are easily combined with mineral wool filled panels or double wall panels to solve a wide variety of sight and sound problems.
● Reflective Panels
Silent Screen Reflective Panels are designed to provide sound transmission loss only. The panels consist of interlocking sections, typically 12 inches wide, and can be mounted horizontally or vertically. Reflective panels provide a lightweight, aesthetically pleasing noise wall and acoustical barrier.
● Mass Loaded Vinyl Noise Barrier
Characteristic features
• Reduces Sound Transmission • Contains Noise • Improves Communications • Improves Health & Safety2 lb. PSF / 16 / 22 / 26 / 32 / 35 / 40 / 311.25 lb. PSF / 14 / 18 / 24 / 27 / 33 / 38 / 28
1 lb. PSF / 13 / 17 / 22 / 26 / 32 / 37 / 26
1/2 lb. PSF / 8 / 13 / 17 / 22 / 27 / 31 / 20
Picture showing the sound transmission loss of vinyl noise barrier
Transmission loss through glass
Glass is a universally used material with very reflective properties. It is in most cases used as curtain walls, as covering to windows as well as doors. It acoustic properties vary according to its sizes and constituents.
Below are the acoustic properties of glass of different sizes, Glass type / configuration / Average STC (dB) / STCRating / RW
(dB) / PSR
%perceived sound reduction
3mm flat / 24 / 26 / 26 / 0
12mm flat / 32 / 36 / 36 / 50
6.76mm PVB laminated / 3mm/0.76mm/3mm / 31 / 35 / 35 / 45
10.76mm PVB
laminated / 5mm/0.76mm/5mm / 35 / 37 / 37 / 52
9mm stop sound / 4mm/1.0mm/4mm / 35 / 37 / 37 / 53
17.4mm Glass tech / 6.38mm/6mmAS/5mm / 32 / 35 / 35 / 45
112 double window / 7mm sound stop/110AS/5mm / 48 / 50 / 50 / 80
Glass block / 190x190x80mm / 40 / 42 / 42 / 65
4.0 CONCLUSION
In accordance with the aforementioned principles, examples of building materials and their functions. It can be said; to achieve an acoustically stable room that will enhance speech intelligibility, the need for the proper selection of building material cannot be overemphasized. Therefore the study of acoustics as well as the study of materials to enhance should be promoted in schools of higher learning.
5.0 RECOMMENDATIONS
Since one of the main goals of architectural acoustics is to provide optimum speech intelligibility and sound quality in auditoriums of public buildings, acoustical input is required in the construction of new buildings and during the refurbishment of existing buildings whether they are general purpose or specialized facilities.
The acoustical inputs therefore include the use of materials that are can ensure good absorption, reflection, transmission and diffusion of sound in order to eliminate the problems of reverberation and echoes and achieve an equal sensory of sound by an audience at different locations within the hall.
It is recommended that an acoustician be consulted for professional advice on design and the use of materials that have good acoustic properties in order to help optimize acoustics since the success of an acoustical design depends to a considerable extent upon how completely the acoustician's recommendations are followed in carrying out the design. Ignoring, or partial acceptance of recommendations usually leads to acoustical deficiencies in the hall.
6.0 REFERENCES
Architectural Surfaces, Inc,
Acoustical Surfaces, Inc. 15
Mazer, S. E. (2005, March/April). Reduce errors by creating a quieter hospital environment. Patient Safety & Quality Healthcare. Retrieved March 25, 2010, from
Ryherd, E. E., Waye, K. P., & Ljungkvist, L. (2008). Characterizing noise and perceived work environment in a neurological intensive care unit. Journal of the Acoustical Society of America, 123(2), 747-756.
Daly, P. (2009, June 15). Shhhh! Hospital acoustic upgrades under construction. Grand Rapids Business Journal.Retrieved March 3, 2010, from
RWDI Consulting Engineers (n.d.). Noise and acoustics for healthcare design. Technotes, 32. Retrieved March 3, 2010, from
Busch-Vishniac, I., West, J., Barnhill, C., Hunter, T., Orellana, D., & Chivukula, R. (2005). Noise levels in Johns Hopkins Hospital. Journal of the Acoustical Society of America, 118(6), 3629–3645.
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