Uniform Fourier-magnitude diffusion structures scatter sound evenly at any incidence angle.

Evidence

For a diffuser we wish to have a P k ( ) θ that is uniform with respect to angle. This corresponds to a pattern of coefficients. This corresponds to a diffuser structure that has a constant Fourier transform magnitude over the visible region. The effect of an obliquely incident wavefront is to add an additional progressive phase shift across the diffuser’s reradiated sound. This causes the visible region to be shifted in angle. Therefore, in addition, we would like the Fourier transform magnitude to be uniform outside the visible region as well to cover oblique incidence. Therefore, we need to find diffusion structures that have uniform-magnitude Fourier transforms, such as Schroeder (Schroeder, 1975) diffusers. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2899

Categorization

• DEFINE: Introduces the definition of a ‘diffuser’ as a structure whose polar response is uniform with angle, and the oblique-incidence problem it must solve.