A modified evaluation of energy parameters in ODEON 1.1 using Sabine’s diffuse energy decay formulas

Abstract

The lack of diffuse reflection in a room acoustic computer model ODEON 1.1 [created by Tech. Univ. of Denmark] is considered as one major technical shortcoming. This can lead to very poor estimation of the reverberation behavior of the room whose geometry is itself poorly diffusive. In order to overcome this problem, surfaces are considered to be partially specularly and partially diffusely reflecting, as quantified by absorption coefficient a and diffusion coefficient d, respectively. The diffuse energy, i.e., a proportion d(1−a) of the incident energy, is assumed to be distributed uniformly inside the room and accumulating in an imaginary pool. By using Sabine diffuse energy decay formulas: E(t)=E(t0)exp[−(t−t0)/τE], the diffuse sound energy coming into pool at any time t can be calculated. Thus the total diffuse energy accumulated in the pool at certain time t is added to the nondiffuse energy, and taken into account in evaluation of energy parameters. The prediction of RT and EDT in midfrequencies give better agreement with measured RT and EDT made in rectangular 1:50 model room, than those of origin program. [Research project for Master degree, supervised by Dr. Y. W. Lam.]