Diffuse-field assumptions hold at high frequencies but break down at low ones

Evidence

Therefore one must take note of an important assumption behind Equation 6.6, which is that the reverberant sound visits all surfaces with equal probability and from all possible directions. This is known as the “diffuse field assumption.” It can also be looked at as a definition of a diffuse field. In general, the assumption of a diffuse field is reasonable, and it is usually a design goal for most acoustics. However, it is important to recognize that there are situations in which it breaks down, for example at low frequencies. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1774

Categorization

• DEFINE: Defines the diffuse field assumption precisely: reverberant sound visits all surfaces equally from all directions.
• XREF: Connects to the reader’s interest in listening environments — explains why a room’s reverberation behaves differently at low frequencies than high ones. — connects to: Modal behavior makes diffuse-field analysis fail in a mid frequency range — David Howard, Jamie Angus, coustics and Psychoacoustics, 2073