Sound Field Diffuseness in Oblique-Shaped Reverberation Rooms with Different Test Configurations

Résumé

The reverberation-room method, which assumes a diffuse sound field, has long been used for various standardized room-acoustical determinations – e.g. of surface-absorption coefficients, power levels of sound sources, transmission losses of acoustical partitions, etc. However, despite the existence of a number of standards, those outline guidelines to conduct reverberation-room measurement, the accuracy of the method is still questionable, which could be attribute to the insufficient field diffuseness. To investigate the problem and propose solutions, an oblique-shaped reverberation room with the shortest vertical dimension and ISO prescribed size of 150 m³ is considered for six different configurations: empty, with diffusers, with absorbent corner treatment, with diffuse surface reflection, with diffusers and absorbent corner treatment and with diffusers and diffuse surface reflection. A numerical finite-element-based modal approach has been utilized, and a number of room acoustical parameters have been used as descriptors to quantify the degree of sound field diffuseness. Analyzing the results, it has been found that the rooms with diffusers and absorbent corner treatments yield improved sound-field diffuseness, hence better prediction accuracy, while the rooms with diffuse surface reflection yield poor field diffuseness due to the increased surface absorption.