Absorption Coefficient
The fraction of incident sound energy absorbed by a material surface rather than reflected.
Governing formula
α = I_absorbed / I_incident (0 ≤ α ≤ 1)
SI unit
Dimensionless
In depth
A coefficient $α = 1$ represents a perfect acoustic absorber (100% absorption); $α = 0$ represents a perfect reflector.
Examples in the real world
Acoustic foam wall panels having $α ≈ 0.9$ at high frequencies to eliminate echoes in recording studios.