AN APPLICATION OF ACOUSTIC FINITE-ELEMENT MODELS TO FINDING THE REVERBERATION TIMES OF IRREGULAR ROOMS

A new finite element method, previously tested on regular shaped rooms , is applied to finding the effects on the reverberation times of comm on irregularities like curved surfaces, non-parallel walls and large o pen-walled ante-rooms, found in auditoria. The number of modes having a reverberation time in a specified time interval is expressed as a fu nction of the total allowed degrees of freedom and it is shown that ev en when the number of degrees of freedom of the model is large there i s, in general, no one dominant group. Curved surfaces in particular le ad to a situation where some modes have very long reverberation times, leading to bad acoustics. In such situations a knowledge of the offen ding mode shapes give an indication on where to position absorptive ma terial for optimum effect.