Diffusion equation-based modelling of reverberation chambers for sound absorption measurements

Abstract

Recent research in reverberation chambers has revealed unacceptably large variations resulting from round-robin tests of the standardized measurements of random-incidence absorption coefficients. These variations have prompted active research activities in architectural acoustics. This study applies a diffusion equation model (DEM) in acoustics of reverberation chambers for random incidence absorption measurements by predicting both reverberant sound energies and energy flows. The DEM is of high computational efficiency when compared with other existing geometrical acoustics and wave-based methods. The DEM modeling of the sound energy flows in a reverberation room further reveals violations of the diffuse field assumption near the boundary area of absorbing sample under test. Due to its computational efficiency and higher order of the reverberant energy prediction of the statistical room-acoustic modeling, this work investigates an estimation approach to the absorption coefficients of the sample under test. The proposed approach estimates the absorption coefficients by pursuing both the DEM simulations and the chamber-based measurements. This paper investigates sound energy flux over varied absorbing degrees of absorber samples in standardized sizes, computational efficiency of the DEM for reverberant energy decays in reverberation chambers, and potential significance applied to random-incident absorption coefficient measurements.