Diffuse surfaces scatter sound hemispherically rather than mirror-like

Evidence

Diffuse surfaces, on the other hand, scatter sound in other directions than the specular. In the case of an ideal diffuser, the scattered energy polar pattern would be in the form of a hemisphere. A simple approach to calculating the effect of this can be to model the scattered energy as a source whose initial intensity is given by the incident energy. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2318

Categorization

• DEFINE: Defines the ideal diffuser and the modeling trick of treating scattered energy as a secondary source.
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2318
• XREF: connects to: Reflection from rough surfaces smooths detail once wavelengths exceed roughness; Walls must be rough on many scales to scatter sound diffusely; Flat surfaces reflect low-frequency sound specularly but scatter high-frequency sound (+6 more)