This document discusses two scattering/diffusion coefficients that are used to characterize how sound is reflected from surfaces in rooms. 

The first coefficient, a scattering coefficient, quantifies the amount of sound scattered away from the specular reflection direction based on measurements in a diffuse sound field. An international standard has been established for this coefficient. 

The second coefficient, a diffusion coefficient, measures the spatial uniformity of reflections produced by a surface based on measurements in a free sound field. A definition for this coefficient has been published by the Audio Engineering Society and is being considered by an international standards organization.

The paper aims to explain when each coefficient should and should not be applied, as well as contrast their definitions and performance, as

COX - A Tutorial On Scattering and Diffusion Coefficients For Room Acoustic Surfaces (2006) PDF

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