The absorption coefficient α is a property of a material. It defines the extent to which a material absorbs energy, for example that of sound waves or electromagnetic radiation. Wallace Sabine was a pioneer of this concept in acoustics and defined the unit of the Sabine. A Sabine is defined as a fraction of acoustic power absorbed by a 1m square of open window. In SI units, absorption coefficient is measured in inverse metres, and is represented by the Greek letter α. Sound Absorption Coefficients for Some Common Materials - This website helps one understand the concept as well as provides formulae and some coefficients. In chemistry and biological sciences, the absorption coefficient is a measure of the solubility of a gas in a liquid measured as the volume of the gas (taken under standard conditions) that saturates a unit volume of the liquid. Absorption coefficient is sufficient for describing energy propagation through a homogeneous system only. Propagation through a heterogeneous system is affected by scattering,[1]. There is more general term attenuation that takes into account both absorption and scattering. It is widely used in acoustics as attenuation coefficient for characterizing particle size distribution. [2],[3].
