A form of acoustic panel employed in the acoustic treatment of a room which reflects incident sound in specific ways with the aim of maintaining an even spread of sound energy withint he environment.
There are many different forms of diffusor, each with different characteristics, but the two most common are:
MLS or Maximum Length Sequence diffusors: constructed from parallel strips of material creating a surface at two different depths. The strip widths are smaller than, or equal to, half the wavelength of the frequency where the maximum diffusion effect is required, and the effective bandwidth of this design is typically only an octave.
QRS or Quadratic-residue diffusors are similar to MLS panels, but are effective over a much wider bandwidth which is achieved by employing a larger number of depth variations. Available in 2D (strips) and 3D (blocks or 'skyline') versions to reflect sound in one or two axes respectively. Also known as a Schroeder diffusor.