Reverberation in rectangular long enclosures with diffusely reflecting boundaries

Based on the technique of radiosity, a computer model has been developed for calculating acoustic indices in rectangular enclosures with diffusely reflecting boundaries. The model divides every boundary into a number of patches and replaces patches and receivers with nodes in a network. The effectiveness and accuracy of the model have been demonstrated in several enclosures. For a number of hypothetical long enclosures with diffusely reflecting boundaries computations using the model show that: with the increase of source-receiver distance the RT30 increases continuously and the early decay time (EDT) increases rapidly until it reaches a maximum and then decreases slowly; the decay curves are concave in the near field and then become convex; with a constant cross-sectional size, both the RT30 and EDT reach their maximum as the aspect ratio tends to 1; and with a given amount of absorption, the reverberation varies considerably with different absorber distributions in cross-section. For diffusely as opposed to geometrically reflecting boundaries, the sound attenuation along the length is notably greater, and air absorption is more effective with regard to both reverberation and sound attenuation.