Sound Absorption Coefficients for some common Materials

Sound absorption coefficients for some common materials as plaster walls, brickwork, plywood panels etc...

The sound absorption coefficient indicates how much of the sound is absorbed in the actual material. The absorption coefficient can be expressed as: 

α = Ia / Ii        (1)

where 

Ia = sound intensity absorbed  (W/m2)

Ii = incident sound intensity  (W/m2)

 Absorption coefficient - α - for some common materials can be found in the table below:

MaterialSound Absorption
Coefficient
- α -
Acoustic belt, 12 mm 0.5 - 0.5
Acoustic tiles 0.4 - 0.8
Asbestos, sprayed 25 mm 0.6 - 0.7
Brickwork, painted 0.01 - 0.02
Brickwork, unpainted 0.02 - 0.05
Cork sheet, 6 mm 0.1 - 0.2
Fiberboard on battens, 12 mm 0.3 - 0.4
Hardwood 0.3
Mineral wool, 100 mm 0.65
Persons, each 2.0 - 5.0
Plaster walls 0.01 - 0.03
Plywood panel, 3 mm 0.01 - 0.02
Polystyrene, expanded on 50mm battens 0.35
Polystyrene, expanded rigid backing 0.15
Polyurethane foam, flexible 0.95
Rubber sheet, 6 mm porous 0.1 - 0.2
Slag wool or glass silk, 50 mm 0.8 - 0.9
Snow 0.75
Wood wool cement on battens, 25 mm 0.6 - 0.07

Note! The absorption coefficient varies with the frequency of sound. 

Total Room Sound Absorption

The total sound absorption in a room can be expressed as: 

A = S1 α1 + S2 α2 + .. + Sn αn = ∑ Si αi       (2)

where 

A = the absorption of the room (m2 Sabine)

Sn = area of the actual surface (m2)

αn = absorption coefficient of the actual surface

Mean Absorption Coefficient 

The mean absorption coefficient for the room can be expressed as:

am = A / S      (3)

where

am = mean absorption coefficient

A = the absorption of the room (m2 Sabine)

S = total surface in the room (m2)

A rooms acoustic characteristics can be calculated with the formulas above, or estimated for typical rooms.

Related Topics

  • Acoustics - Room acoustics, acoustic properties - decibel A, B and C - Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity, attenuation and more
  • Noise and Attenuation - Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems

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