Scattering and diffusion of sound play an important role in room acoustics.

In practical applications as well as in computer simulations this effect must be taken into account properly. Surfaces with corrugations, ornaments, sculptures and surfaces with finite size will give a certain amount of diffusion and scattering. When scattered, incident sound is not re-directed in a direction according to the specular path, but distributed in spatial angles in a particular way. For quantitative characterisation of scattering, two quantities were defined and standardised in two parts of ISO 17497, namely the scattering coefficient and the diffusion coefficient. The scattering coefficient quantifies the amount of sound energy scattered, but gives no information about the specific directional distribution. The diffusion coefficient quantifies the uniformity of the polar scattering distribution. Both quantities have their specific field of application. The measurement procedures, the results and applications of scattering and diffusion will be presented and discussed.