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Absorption refers to the absorption of sound waves by a material. The absorption is the "missing piece", when comparing the total reflected and transmitted energy with the incident energy.

It is the property of a material that changes acoustic energy into usually heat energy. A material or surface that absorbs sound waves does not reflect them. Absorption of a given material is frequency-dependent and is affected by the size, shape, location, and mounting method used.

A good sound absorber is normally a porous material. Mineral wool, glass wool, and micro perforated plates work as sound absorbers.

Absorption is not a single mechanism of sound attenuation. Propagation through a heterogeneous system is affected by scattering as well.

Acoustical absorption is represented with the symbol A.

Acoustical absorption in the ocean is an important part of the analysis of sonar. The primary substance in seawater that is responsible for absorption is magnesium sulfate. The secondary substance is boric acid. The most common sea salt, sodium chloride has virtually zero effect on sound absorption.

[edit] See also

• Absorption coefficient
• Acoustic board
• Attenuation coefficient
• Anechoic chamber