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 dependant as well as being affected by the size, shape, location, and mounting method used.

See also absorption coefficient The extinction coefficient for a particular substance is a way of measuring how well electromagnetic radiation is absorbed at a particular wavelength. ...