Sound Diffusion

Sound diffusion is the scattering of reflected sound energy in many directions rather than in a single specular direction. A perfectly diffuse sound field has uniform energy density and random incidence at all points, which is the underlying assumption of the Sabine and Eyring equations. In practice, diffusion is achieved using irregularly shaped surfaces, purpose-built diffusers (QRD, Schroeder, skyline), bookshelves, coffered ceilings, and other surface modulation with dimensions comparable to the wavelengths of interest. Good diffusion improves spatial uniformity, reduces flutter echoes, enhances envelopment in concert halls, and helps achieve consistent reverberation decay. The degree of diffusion can be quantified using the diffusion coefficient per ISO 17497-2 or the scattering coefficient per ISO 17497-1. Diffusion is distinct from absorption: diffusers redistribute energy without removing it, maintaining the room’s liveliness while improving uniformity.