The property of surface by which sound energy (kinetic energy) is converted into other form of energy, generally heat energy (due to friction) and get absorbed. There is no royal road for making a particular room acoustically good. It mainly depends on the ideas of the engineer or the Architect. Each case is to be studied separately and after proper thinking and calculations, suitable materials may be specified.

1. SOUND
ABSORPTION &
ABSORBERS
PRESENTED BY:
ROHIT BHATT
B-ARCH 4TH SEM
K.C.A.D., BAREILLY
PRESENTED TO:
AR.MALVIKA SRIVASTAVA
BUILDING SERVIC

2. SOUND ABSORPTION
• The property of surface by which sound energy (kinetic
energy) is converted into other form of energy, generally
heat energy (due to friction) and get absorbed.
• The degree to which this surface affects the absorption of
sound is known as absorption coefficient.
• There is no royal road for making a particular room
acoustically good. It mainly depends on the ideas of the
engineer or the Architect. Each case is to be studied
separately and after proper thinking and calculations,
suitable materials may be specified.

3. REQUIREMENTS OF A GOOD SOUND
ABSORBENT:
 It should be
 Durable,
 Vermin-proof,
 Efficient over wide range of frequencies,
 Fire-resistant,
 Non- Hygroscopic and heat insulating,
 Self- supporting and Easly fixable,
 Pleasing in appearance,
 High coefficient of absorption,
 Sufficient structural strength.

4. TYPES OF SOUND ABSORBING
MATERIALS
According to their physical composition,
 POROUS MATERIALS
 NON- PERFORATED OR MEMBRANE ABSORBERS.
 CAVITY OR HELMHOLTZ RESONATERS

5. POROUS MATERIALS
 Basic acoustical characteristic of all porous materials is a cellular
network of minute interlocking pores.They convert the incident
sound energy into heat energy by the frictional and viscous
resistance within these pores and by vibration of their small fibres.
Good for high frequency range.
• Fibreboards, mineral wools, insulation blankets, etc. are some of the
examples
Glass WoolRock wool

6. NON PERFORATED PANELS &
MEMBRANE ABSORBERS
 Any impervious material, installed on a solid backing but separated
from it by an air space, will be set to vibration when struck by sound
waves. Good for low frequency range.
 Wood and hardboard panelling, gypsum boards, suspended plaster
ceilings, furred out plasters, rigid plastic boards, windows, glazing,
doors, wood floors and plat-forms, etc
Gypsum Boards

7. CAVITY OR HELMHOLTZ
RESONATERS
 They consist of an enclosed body of air confined within rigid
walls and connected by a narrow opening(called the neck) with
the surrounding space in which the sound waves travel.
 Cavity resonators can be applied
1. As individual units
2. As perforated panel resonators
3. As slit resonator panels.

8. TYPES OF SOUND ABSORBING
MATERIALS
According to their trade name and availability in market,
 HAIRFELT,
 ACOUSTIC PLASTER,
 ACOUSTICAL TILES,
 STRAWBOARD,
 PULP BOARDS,
 COMPRESSED FIBREBOARDS,
 COMPRESSED WOOD PARTICLE BOARDS,
 PERFORATED PLYWOOD,
 WOOD WOOL BOARD,
 QUILTS AND MATS.

9. HAIRFELT:
 The material was used by prof. Sabin in his experimental
works, made up of wool anf fur.
 The average value of coefficient of absorption of 25mm thick
hairfelt is 0.60.
 It is used at rooms and halls.

10. ACOUSTIC PLASTER
 Also known as the fibrous plaster and it includes granulated
insulation insulation material mixed with cement.
 The average value of coefficient of absorption of 20mm thick
and density of 1kN/m3 acoustic plaster is 0.30 at 500 cps.
 For acoustical plaster boards- 0.15-0.30

11. ACOUSTICAL TILES
 They are factory made, uniform sound absorbers, easily fixable
but expensive.
 Most suitable for rooms in which small area is available for the
acoustical treatment.

12. STRAWBOARD
 Prepared from compressed straw and covered with thick
paper or hardboard are used.
 The average value of coefficient of absorption of 13mm
thick and density of 12.4kN/m3 is 0.3 at 500 cps.
 It is used at rooms and medium capacity halls.

13. PULPBOARDS
 These are the softboards prepared from compressed pulps.
 The average value of coefficient of absorption of 13mm thick,
is 0.17 at 500 cps.
 They are cheap and can be fixed by ordinary panelling.

14. COMPRESSED FIBREBOARD
 Made up of compressed fibre, may be perforated or
unperforated.
 The average value of coefficient of absorption of perforated
one with the density of 3kN/m3 is 0.30 and of other one is 0.52.

15. COMPRESSED WOOD PARTICLE
BOARD
 Prepared from compressed wood and provided with
perforations and it can be painted also.
 The average value of coefficient of absorption of 13mm
thick is 0.40 at 500 cps.

16. PERFORATED PLYWOOD
 Can be used by forming composite panels with mineral wool and
cement asbestos or with mineral wool and hardboard.
 Generally suspended from trusses.
 The average value of coefficient of absorption for the former one
is as high as 0.95 and for the latter one, it is about 0.20.

17. WOOD WOOL BOARD
 Prepared from a mixture of portland cement and wood
wool or wood shavings. A small quantity of Gypsum is
sometimes added.
 The average value of coefficient of absorption of 25mm
thick and density of 4kN/m3 is 0.20 at 500 cps.
 It is used at

18. QUILTS AND MATS
 Prepared from mineral wool or glass wool and are fixed in
the form of acoustic blankets
 The absorption coefficients of such quilts and mats depend
on the tickness, density, perforations, mode of fixing, nature
of backing and frequency of sound.

19. THANK YOU!!
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