Avaliação da difusão sonora de uma câmara reverberante em escala reduzida a partir da utilização de diferentes geometrias e configurações de difusores sonoros

Abstract

The formation of sufficiently diffuse sound field is indispensable for determination of important acoustic parameters in reverberation chambers, since such condition represents one of the paramount premises for validating the Sabine Equation for reverberation time. In practice such a condition is usually achieved by the use of sound diffusers inside the acoustic chambers. However, determining the degree of sound diffusion, due to the insertion of diffusers, is a complex task because there are only indirect methods for this purpose, i. e., from the calculation of diffusion indicators. Recent studies indicate that many of the commonly used indicators, even those ones recommended by important standards, do not provide unambiguous results. Additionally, the sound diffusion depends on several factors: (i) the environment (inclination and material of the walls), (ii) the diffusers employed (geometry, material, position relative to the source, etc.), and (iii) the condition incident sound wave, which makes the process of evaluating accurately sound diffusion in reverberant environments even more difficult. The present work evaluates the sound diffusion of different types and geometries of sound (suspended and volumetric) diffusers, in varied configurations, in a scale model reverberant chamber by means of sound absorption coefficient indicator (α𝑚é𝑑), defined according to ISO 354: 2003. The performance of the different diffuser configurations tested is discussed in some detail, as it is found that the highest degree of diffusion is directly related to the largest relative surface area of diffusers, due to the greatest scattering. Finally, volumetric diffusers presented similar performance to hanging diffusers, but with significantly smaller relative surface area, indicating this type of diffuser is more efficient in increasing the sound diffusion than hanging ones, even in small cameras.