The development and use of the diffusion scattering coefficients in room modeling software: The effect of diffuse reflections on reverberation time

Abstract

In the last 20 years, much progress has been made in the measurement and characterization of sound diffusing surfaces. This presentation describes how this research might improve the accuracy of computer based geometric room modeling. To model diffuse reflections, one needs to know the scattering distribution and the portion of scattered energy that is diffusely reflected. AES Working Group SC-04-02 recently published an information document AES-4id-2001, which describes a measurement procedure to determine the polar balloons from scattering surfaces. This allows programmers to use actual measured or calculated distributions instead of Lamberts law, which applies to incoherent optical diffusion. ISO WG 25 is currently addressing a measurement procedure to determine the random incidence scattering coefficient. This scattering coefficient is used directly in geometrical modeling programs. The two measurement procedures will be contrasted. It will then be demonstrated by example how the use of diffusion data can affect the predicted reverberation time.