Scattering Coefficient

The scattering coefficient (s) quantifies the fraction of reflected sound energy that is scattered in non-specular directions by a surface, ranging from 0 (perfect specular reflection) to 1 (complete diffuse scattering). Defined in ISO 17497-1:2004, it is measured by comparing the reverberation time of a room with a flat test surface to the reverberation time with the test surface rotated on a turntable to create angular averaging. The scattering coefficient is used in geometric room acoustic simulation software (ray tracing, image source) to model the diffusing properties of surfaces. Assigning appropriate scattering coefficients to room surfaces significantly affects simulation accuracy, particularly for late reverberation and spatial metrics. Typical values range from 0.05 (smooth painted wall) to 0.70 (heavily profiled surface). The scattering coefficient is frequency-dependent, generally increasing with frequency as surfaces become rougher relative to the wavelength.