Correspondence between reflected and incident pulse signals on acoustic diffuse surfaces

Abstract

The reflection coefficient of acoustic diffuse surfaces shows at high frequencies unreasonable values greater than unity due to the promoted sound scattering. Aiming an adequate assessment of the reflection of such surfaces, it is proposed to quantify the correspondence (i.e. the similarity) between reflected and incident signals of impulse responses from diffusers. The product between a (specular or scattered) reflected pulse and a synchronized and weighted incident pulse, acquired without surface, results in a mutual correspondence signal. This measure is normalized by the square of this adjusted incident pulse, a standard autocorrespondence signal. In principle, the ratio between the spectral amplitudes of the resulting signals provides a corresponding reflection factor, which indicates the correspondence between the reflected and the incident sound pressure synchronized pulses. Analyses are done from measurements of normal incidence on samples of corrugated diffuse surfaces, including different incidence regions, besides a flat surface. It is shown that for diffuse surfaces, unlike the reflection coefficient, the proposed factor supplies good values along all over the spectrum. These results suggest the possibility of applying this parameter for the evaluation of sound reflection and diffusion of such surfaces.