A new scattering method that combines roughness and diffraction effects

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 dimension, 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: (a) Separating the user specified surface scattering coefficient from the room geometry, makes it easier for the user to make good guesstimates of the coefficients which will be in better agreement with the ones which can be measured. In many cases a scattering coefficient of say 1% for all surfaces may be sufficient. (b) Scattering due to diffraction is distance and angle dependent and as such it is not known before the actual raytracing or image source detection takes place. An example of this is that a desktop will provide a strong specular component to its user whereas it will provide scattered sound at far distances.