Sound Absorption Coefficient
The sound absorption coefficient (α) describes what fraction of sound energy hitting a surface is absorbed rather than reflected. It ranges from 0 (fully reflective, like a bare concrete wall) to 1 (fully absorptive, like an open window), and is calculated as α = 1 − (Ireflected / Iincident).
Acoustic engineers use this value, often measured per frequency band, to design room treatments, concert halls, and noise barriers. Soft, porous, and fibrous materials (foam, carpet, curtains) generally have higher absorption coefficients than hard, dense, flat surfaces.
Last reviewed August 2026