Optimized diffusers for shoe-box shaped performance halls

Abstract

Sound diffusion is a very important parameter in an overall assessment of the quality of an auditorium. This is why, the use of sound diffusers, especially sound phase diffusers, has been gaining more and more popularity. The most common structures are PR and QR diffusers. However, it was noted that the diffusers should be designed not only based on their diffusion and scattering coefficients, but also other parameters (e.g. sound absorption) determined with regard to the location of a diffuser in an auditorium. In this paper, the optimization algorithms are used for the designs of the diffusers. Different objective functions are proposed, depending on the locations of the diffusers in a typical shoe-box shaped performance hall, i.e., minimizing sound absorption coefficient, reduction of specular reflection, and intentional redirection of reflections. In the paper, a structure of 2 × 11 wells of amaximum depth of 0.15 m, and of a total width of 0.6 m is optimized. The final structures are significantly better than the commonly used PR and QR diffusers of similar dimensions in terms of the acoustic performance, with regard to their location. The presented methodology can be used for designing precise sound diffusers made of different base elements, e.g., quarter-wave diffusers or metamaterials, specific for each application.