Coupling Coefficient of Flux Density and Density Gradient of Reflected Sound Energy in Quasi-Diffuse Sound Fields

Abstract

Sound pressure levels in rooms are determined by the energy of direct sound and the energy generated by reflections of sound from enclosures. In some areas of a room, the reflected sound energy exceeds the energy of the direct sound. For this reason, calculations of the energy characteristics of reflected sound energy are of great importance. In most rooms, the reflection of sound from enclosures has a specular-diffuse character. In this case, one part of the reflected energy transferred by specular reflected waves is distributed according to the laws of geometric acoustics, and the other part, scattered diffusely, according to Lambert’s law. The calculation of the specular component of the reflected energy is made by the methods of ray tracing, and the scattered energy is calculated by the statistical energy methods developed by the authors for the quasi-diffuse sound fields of the rooms. The basis of the latter methods is the relationship between the flux density of reflected sound energy and the density gradient of this energy. The accuracy of these methods depends on the accuracy of the adopted value of the coupling coefficient between the flux density and the density gradient of the reflected sound energy. Currently, there are different ideas about its magnitude. The paper presents the results of studies of coupling coefficients with regard to space-planning and acoustic characteristics of premises. The investigations were carried out using Kuttruff’s integral equation. Based on the results obtained, recommendations are given on the choice of the coupling coefficient.