Modern acoustic diffusion uses mathematically structured well patterns

Evidence

Clearly effective diffusion is a difficult thing to achieve in an ad hoc manner. Curved and angled structures can help at mid and high frequencies, and at very high frequencies, greater than about 4 kHz, the natural rough textures of materials such as brick and rough-cut stone are effective. Because of the need to achieve well-defined diffusion characteristics, diffusion structures based on patterns of wells whose depths are formally defined by an appropriate mathematical sequence have been proposed and used (Schroeder, 1975; D’Antonio and Konnert, 1984). — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2072

Providing diffuse reflections is thus important, and this has been recognized for some time. Traditionally, plaster mouldings, niches, and other decorative surface irregularities have been used to provide diffusion in an ad hoc manner. More recently, diffusion structures based on patterns of wells whose depths are formally defined by an appropriate mathematical sequence have been proposed and used. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1927

Categorization

• DEFINE: Introduces Schroeder diffusers, a key technical term in acoustic room treatment.
• SEED: Great angle for a piece on how old concert-hall plasterwork accidentally did the job that modern acoustic diffusers now do deliberately.
• ADDENDUM: Rhymes with ‘Grafting & Growth’ themes: decorative surface irregularities functioning as invisible functional infrastructure.
• corroborated: 3 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2072; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1927
• XREF: connects to: Acoustic diffusion needs surface bumps sized between an eighth and a half wavelength; Effective sound diffusion demands surface depths proportional to the target wavelength; Sequences whose autocovariance approximates a delta function make effective sound diffusers (+3 more)

Broader Connections

• Sequences whose autocovariance approximates a delta function make effective sound diffusers #corroborates (0.88)
• m-sequences offer flat Fourier properties suited to diffusion design #corroborates (0.85)
• Acoustic diffusion needs surface bumps sized between an eighth and a half wavelength #expands (0.82)
• Binary amplitude sequences can represent reflection and absorption in diffuser design #expands (0.80)
• Effective sound diffusion demands surface depths proportional to the target wavelength #qualifies (0.75)