Reverberation-Room Measurement Assuming a Diffuse Sound Field: Reviewing Standards and Reality

摘要

The diffuse-field assumption in reverberation-room measurements may be misleading, asthere is no straight-forward way to characterize sound field diffusivity. In this regard,standards offer some help outlining necessary conditions to achieve sufficient diffusion;however, measurement accuracy is still unsatisfactory. To investigate the problem and findan optimal solution, existing standards have been revisited, and their contribution toachieving a diffuse field is analyzed in this paper. Results obtained by computer simulationare discussed; in particular, the minimum approachable frequencies of measurements anddegree of field diffusivity are explained in detail using descriptors like spatial uniformity ofpressure and decay rates, degree of linearity of decay curves, directional uniformity ofpropagating modes, etc. The results obtained are mostly accurate at higher frequencies,indicating that the field is sufficiently diffuse in that range, and at the same time, revealingthe shortcoming of the standards to provide low-frequency diffusion. Based on thesefindings, an attempt is made to reinforce the existing standards by outlining ways topromote the low-frequency diffusion. With the help of a numerical modal approach, a mostprobable way of approaching the low-frequency limit of a diffuse field in reverberationrooms is discussed.