Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Sound - Room Absorption Coefficients

Sponsored Links

The sound absorption coefficient is the ratio of absorbed sound intensity in an actual material to the incident sound intensity and can be expressed as

α = Ia / Ii                                (1)

where 

α = sound absorption coefficient

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:

Sound - Room Absorption Coefficients
MaterialSound Absorption
Coefficient 1)
- α -
Acoustic belt, 12 mm 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
Carpet, heavy on concrete 0.3 - 0.6
Carpe, heavy on foam rubber 0.5 - 0.7
Concrete block, coarse 0.3 - 0.4
Concrete block, painted 0.05 - 0.07
Cork sheet, 6 mm 0.1 - 0.2
Fiberboard on battens, 12 mm 0.3 - 0.4
Floor, concrete or terrazzo 0.02
Floor, linoleum, asphalt, rubber or cork tiles on concrete 0.03
Floor, wood 0.06 - 0.1
Hardwood 0.3
Glass, large panes heavy plate 0.03 - 0.05
Glass, ordinary windows 0.1 - 0.2
Gypsum board, 12 mm 0.04 - 0.07
Mineral wool, 100 mm 0.65
Persons, each 0.2 - 0.5
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

1) Note! - the sound absorption coefficient varies with frequency. 

Download and print Room Sound Absorption Coefficient chart

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)

Si = area of the actual surface (m2)

αi = absorption coefficient of the actual surface

Mean Absorption Coefficient 

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

αm = A / S                                 (3)

where

αm = mean absorption coefficient

S = total surface in the room (m2)

The acoustic characteristics of a room can be calculated with the formulas above, or estimated for typical rooms.

Example - Room Acoustic Absorption

The total sound absorption in a room with

  • 10 m2 concrete floor with absorption coefficient 0.02
  • 10 m2 concrete roof with absorption coefficient 0.02
  • 40 m2 fiberboard walls with absorption coefficient 0.3

can be calculated as

A = (10 m2) (0.02) + (10 m2) (0.02) + (40 m2) (0.3)

   = 12.2 m2 Sabine

The mean absorption coefficient can be calculated as

αm = (12.2 m2 Sabine) / ((10 m2) + (10 m2) + (40 m2))

     = 0.2

Sponsored Links

Related Topics

Acoustics

Room acoustics and acoustic properties. decibel A, B and C calculations. Noise Rating (NR) curves. Sound transmission through walls. Calculate sound pressure, sound intensity and sound attenuation.

Noise and Attenuation

Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.

Related Documents

Maximum Sound Pressure Levels in Rooms

Maximum recommended sound pressure levels in rooms like kindergartens, auditoriums, libraries, cinemas and more.

Propagation of Sound Indoors - the Room Constant

In a room the sound or noise will reach the receiver as direct and reverberant sound.

Sound - Reverberation Time

The sound reverberation time indicates how long it takes until the sound pressure level in a room is decreased with 60 dB.

Sound - Room Absorption Characteristics

Mean absorption coefficients and reverberation times in typical rooms.

Sound - Room Attenuation in Direct Sound Fields

Room size, absorption characteristics - and attenuation in direct sound fields.

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.