A

WRITE – UP

ON

ACOUSTIC PROPERTIES

OF

BUILDING MATERIALS

COMPILED BY

ARC/01/9223 IJATUYI Olufunto T

ARC/01/9246 OYEKU Mobolaji J.

ARC/03/1930 ODUBENA Olawale O

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 APRIL 2007

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

ii

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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1.0 INTRODUCTION

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.

1

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

2

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

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;

4

● 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

5

Graph showing absorption coefficient in relation to their frequencies

Sound Silencer ™ Acoustic Ceiling Tiles - Sound Absorption / Noise Reduction

Mount 125Hz 250Hz 500Hz 1KHz 2KHz 4KHz NRC 1” 2”

Ceiling E400

Ceiling E400

0.46 0.51

0.59 0.52

0.42 0.52

0.49 0.77

0.760.89

0.860.98

0.55 0.70

Table showing the Sound absorption/ noise reduction of acoustic ceiling tiles

Sound Silencer™ - Sound Transmission Loss (STC) 125Hz 250Hz 500Hz 1KHz 2.5KHz 5KHz STC

1" 2" 1" w/5/8" Gypsum both sides

6 9 27

5 8 27

7 10 29

8 10 31

10 17 32

15 22 45

9 13 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

6

● 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

7

• 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 C423-90a

125Hz 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

8

Graph showing absorption coefficient in relation to their

frequencies

●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

9

INSTALLATION: Hook and loop fasteners, grommet hangers, curtain spanport

hardware.

CURTAIN S.T.O.P.: Sound Transmission Loss - ASTM E90

Frequency 125Hz 250Hz 500Hz 1KHz 2KHz 4KHz STC 1” Thick w/

Barrier 11 16 24 30 35 35 27

2” Thick w/ Barrier

13 20 29 40 50 55 32

CURTAIN S.T.O.P.: Sound Transmission Loss - ASTM C423 F requency 125Hz250Hz500Hz1KHz2KHz 4KHzNRC 1” Thick w/ Barrier 0.12 0.47 0.85 0.84 0.64 0.62 0.70 2” Thick w/ Barrier 0.19 0.99 0.96 0.80 0.57 0.33 0.85 1” Thick w/o Barrier 0.12 0.47 0.85 0.84 0.64 0.62 0.70 2 ” Thick w/o Barrier 0.19 0.99 0.96 0.80 0.57 0.33 0.85 Tables showing the Sound transmission loss of noise barrier quilted curtains

Relationshi fferent frequencies

p graph showing the absorption coefficient at di

10

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

hese

11

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 & Safety

12

Noise Transmission Loss (dB) Per Octave Band (HZ) Barriers

125 250 500 1000 2000 4000

STC

2 lb. PSF 16 22 26 32 35 40 31 1.25 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

Table showing Noise transmission loss of Mass Loaded Vinyl Noise Barrier at

different frequencies

● Description of Mass Loaded Vinyl Noise Barrier

MATERIAL: Mass Loaded Vinyl Barrier

PATTERN: Smooth Finish

FEATURES: High density limp material to reduce noise transmission.

APPLICATIONS: Reduced noise transmission through ceilings, walls, floors,

machinery enclosures, duct- work. Apply over suspended ceilings on studs or

joists.

THICKNESS: 1/16” - 1/2lb./sq.ft. 1/8” - 1lb./sq.ft. 1/4” - 2lb./sq.ft.

SIZES: 54” Wide x 20’, 30’, 60’ Rolls - 2’x2’, 2’x4’ Sheets, Die Cutting Available

COLOR: Black, Grey (Reinforced), Tan and Clear (Transparent or Translucent)

FLAMMABILITY: UL 94VO

INSTALLATION: Material can be nailed, screwed, stapled or can be reinforced

and grometted and hung like a curtain.

13

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)

STC

Rating

RW

(dB)

PSR

%perceive

d 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/5

mm

32 35 35 45

112 double

window

7mm sound

stop/110AS/5mm

48 50 50 80

Glass block 190x190x80mm 40 42 42 65

14

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

www.buildings.com

Architectural Surfaces, Inc,

15

Acoustical Surfaces, Inc.