Absorption Coefficient


The fraction of sound energy that is absorbed at any surface. It has a value between 0 and 1 and varies with the frequency and angle of incidence of the sound.

Measurement Methods
Kundt's tube
Using this method it is only possible to measure normal incidence absorption coefficient. A further development of this is the two microphone measurement.

Reverberation room
Using this method it is possible to measure random incidence absorption coefficient. A more detailed description is given within the section on reverberation time.

There are a number of issues with the measurement of absorption. One of the main problems is mounting the absorptive material the same as the in-use condition.


Factor describing light's ability to be absorbed per unit of path length.

See also: Absorbent Material, Absorption, Linear Absorption Coefficient, Noise Reduction Coefficient, Passive Absorber, Sound, Sound Absorption, Sound Growth.

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Subjects: Noise & Vibration Optics