The concept of diffusion is widely used in many fields, including physics (particle diffusion), chemistry, biology, sociology, economics, and finance (diffusion of people, ideas, and price values). The central idea of diffusion, however, is common to all of these: a substance or collection undergoing diffusion spreads out from a point or location at which there is a higher concentration of that substance or collection.
A gradient is the change in the value of a quantity, for example, concentration, pressure, or temperature with the change in another variable, usually distance. A change in concentration over a distance is called a concentration gradient, a change in pressure over a distance is called a pressure gradient, and a change in temperature over a distance is called a temperature gradient.
The word derives from the Latin word, diffundere, which means “to spread out.”
If an incident sound wave possesses 90 dB of sound energy, a properly diffused reflection will typically possess 85-87 dB of sound energy. Additionally, the angle of reflection is no longer related to the angle of incidence, as the sound is scattered among a wider angle. By its very nature, Diffusion obscures the source location of a sound.
The frequencies affected by a diffuser are related to its size, geometry, material, design, and placement.
Typical diffusing devices include polycylindrical diffusers, quadratic residue diffusers, and reflection phase grating diffusers.