A comparison of three diffuse reflection modeling methods used in room acoustics computer models

Abstract

It is generally believed that partial diffusion will inevitably occur when sound is reflected off a real-life wall. Such diffusion may be caused by the finite size of the wall or by the unevenness of the wall’s surface geometry and/or impedance. Commonly used room acoustics prediction methods such as the image method or the ray-tracing method are usually based on a straight-line geometrically specular reflection model, which must be modified to account for this real-life partial diffusion in order to give realistic results. This paper investigates the problems of the diffuse-reflection coefficient that should be assigned to a wall in auditoria, and the prediction algorithm that may be used to model the diffuse reflections. Acoustic measurement results from scale models and a real multipurpose auditorium were used to compare with the prediction results from three models which used different methods of calculating diffuse reflections. The behavior of these prediction methods and the range of diffuse-reflection coefficients that may be used for different halls is discussed.