Sound absorption refers to the process of reducing sound energy, sometimes by converting it into heat. The term is used very similarly to sound dissipation and insulation. The distinction with dissipation is that it refers exclusively to the conversion into energy other than sound, especially heat, whereas absorption can in principle also refer to other types of “disappearance” of sound (see absorption coefficient). Sound attenuation, on the other hand, refers to any type of reduction in sound intensity which is not necessarily related to a reduction in sound energy, for example by divergence, i.e. by distributing the sound energy over a larger area.
Two variables are used to quantitatively determine sound absorption, the absorption coefficient and the degree of absorption.
As in optics, the absorption coefficient is the exponential coefficient of the decrease in intensity of a plane wave (i.e. without divergence). It is a material constant of the transmission medium during sound propagation. Since this material constant is characterized solely by dissipating absorption, it is practically identical to the dissipation coefficient.
The degree of sound absorption is a measure of the dissipated sound intensity. Sound reflectance is a measure of the intensity of reflected sound. The sound transmission coefficient is a measure of the intensity of transmitted sound. Sound Dissipation Factor is a measure of “lost” sound intensity.
