Influence of the material in the acoustic performance of optimized RBF-based shape diffusers

Sound diffusers are currently a widely used solution in critical listening rooms, in order to reduce specular reflections without introducing excessive sound absorption. There are several types of diffusers on the market, although the most common are derived from the pioneering work of M. Schroeder in this area almost four decades ago. However, the optimization of diffusers' design has been a topic of intense research in the last years. The authors, in previous works, proposed an alternative technique to define new shapes for efficient sound diffusion, based on the use of radial basis functions (RBF) and, using a genetic algorithm, optimized those curvilinear surfaces, maximizing the diffusion coefficient and, at the same time, obtaining organic and more visual appealing acoustic devices. This parameter is computed within the optimization procedure using the Kirchoff integral equation and the Boundary Element Method (BEM). In this work, some solutions developed according to the proposed methodology are presented and the experimental evaluation of some prototypes is carried out, in accordance with ISO Standard 17497-2: 2012, in order to evaluate the influence of the constituent material of the different prototypes. The experimental results are compared with the numerical results obtained in the optimization process.