Predicting Acoustics in Class Rooms

Typical class rooms have fairly simple geometries, even so room acoustics in this type of room is difficult to predict using today's room acoustic computer modeling software. The reasons why acoustics of class rooms are harder to predict than acoustics of complicated concert halls might be explained by some typical features of these rooms; parallel walls, low ceiling height (the rooms are flat) and very uneven distribution of absorption. It is suggested that a part of the explanation to the problem lies in the way scattering is implemented in current models relying on the use of scattering coefficients that are used in order to describe surface scattering (roughness of material) as well as scattering of reflected sound caused by limited surface size (diffraction). A method which combines scattering caused by diffraction due to 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.