Predicting the reverberation time in rectangular rooms with non-uniform absorption distribution

Abstract

This paper proposes a new approach for modelling and predicting the reverberation time in rectangular rooms with non-uniform absorption distribution. The model considers three separate decays for the three room dimensions and a fourth decay for the diffuse field. The sum of the four decays’ RMS-sound pressure values lead to a total decay curve, from which the reverberation time is obtained. Moreover, the model takes into account the absorption coefficients, empirical scattering coefficients at each room surface and lateral sound absorption from side walls. In rooms with a uniform absorption distribution, the calculated reverberation times are similar to those computed by the Eyring’s formula (C.F. Eyring: Reverberation Time in “Dead” Rooms. The Journal of the Acoustical Society of America Volume 1 (1930), p 168). In rooms with a non-uniform distribution, the modeled reverberation times are lengthened, consistent with measurements in previous studies over the whole frequency range. The paper discusses the comparison of calculation and measurement of decay curves and reverberation time, including other well-known simple prediction models.