Most of today’s room acoustics programs make use of scattering coefficients which are used in order to describe surface scattering (roughness of material) and scattering of reflected sound caused by limited surface size (diffraction). A method which combines scattering caused by diffraction due to typical surface dimensions, angle of incidence and incident path length with surface scattering is presented. Each of the two scattering effects is modeled as frequency dependent functions. The benefits are two-fold:

• Separating the user specified surface scattering coefficient from the room geometry makes it
  easier for the user to make good gestimates of the coefficients that will be in better agreement
  with the ones that can be measured. In many cases a scattering coefficient of say 5% for all
  smooth surfaces may be sufficient.
• Scattering due to diffraction is distance and angle dependent and as such it is not known before
  the source and receiver are defined, and the actual ‘ray-tracing’ or image source detection takes
  place. An example on this is that a desktop will provide a strong specular component to its user
  whereas it will provide scattered sound at remote distances.