Reflection from a bumpy surface depends on bump height relative to wavelength.

Evidence

Consider a hard surface consisting of bumps of height d. Also consider an acoustic wavefront approaching it from a normal direction. The way this wavefront is reflected will depend on the height of the bumps relative to its wavelength. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2120

Consider a hard surface consisting of bumps of height d. Also consider an acoustic wavefront approaching it from a normal direction. The way this wavefront is reflected will depend on the height of the bumps relative to its wavelength. Let us consider three cases: ■ In the case of d << λ , the surface will behave like a flat surface and specularly reflect the wavefront. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2073

Categorization

• DEFINE: Sets up the core relationship governing all reflection gratings: bump height versus wavelength decides diffusion behavior.
• corroborated: 2 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 2120; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2073