A material property that describes the internal friction energy loss which occurs in the presence of an acoustic wave. The attenuation depends on the characteristics of the acoustic material (e.g., steel generally has greater attenuation than titanium which has greater attenuation than aluminum). Note that for a "perfect" material (i.e., no energy dissipation) the attenuation is 0.

Also see —
Damping ratio
Log decrement
Loss tangent