Novel scattering coefficient for characterizing diffusely reflecting surfaces

Abstract

In a recent publication (Acta Acustica 103(2017) 480–491), the authors developed an innovative model for describing diffuse sound fields. Developing the diffusion equation one step further, this model makes use of the full stress-energy tensor to provide supplementary relations between sound intensity and sound energy. In the case of non-Sabine spaces (narrow or flat rooms), the supplementary relations naturally introduce new boundary conditions that can be interpreted as scattering coefficients on the walls, in analogy to the traditional absorption coefficients associated with the boundary conditions of the energy equation. The paper explains how the novel coefficient is obtained, compares its significance with the widespread diffuse field wall diffusion coefficient, and proposes an experimental technique for measuring it. Preliminary results will be presented, the expected range of values for the scattering coefficient explained as well as its link to wall impedance in the case of a locally reacting boundary.