The effect of moving microphones and rotating diffusers on the variance of decay rate

Abstract

Methods for reducing the uncertainty of standard building acoustics measurements are of value because they can be used to reduce the time required to obtain a given precision in the measurements. This paper investigates the use of moving microphones and rotating diffusers to reduce the uncertainty of decay rate or reverberation time measurements in a reverberant room. It is shown that in most situations the ensemble variance of decay rate obtained with stationary microphones and diffusers is not affected by the use of a moving microphone or a rotating diffuser. The reduction in spatial variance of decay rate caused by a rotating diffuser previously reported in the literature is observed. A moving microphone reduces the spatial variance at frequencies above 315 Hz. A moving microphone is not as effective as a rotating diffuser in reducing the spatial variance of decay rate.