Energy- and wave-based beam-tracing prediction of room-acoustical parameters using different boundary conditions

Abstract

A beam-tracing model was used to study the acoustical responses of three empty, rectangular rooms with different boundary conditions. The model is wave-based (accounting for sound phase) and can be applied to rooms with extended-reaction surfaces that are made of multiple layers of solid, fluid, or poroelastic materials—the acoustical properties of these surfaces are calculated using Biot theory. Three room-acoustical parameters were studied in various room configurations: sound strength, reverberation time, and RApid Speech Transmission Index. The main objective was to investigate the effects of modeling surfaces as either local or extended reaction on predicted values of these three parameters. Moreover, the significance of modeling interference effects was investigated, including the study of sound phase-change on surface reflection. Modeling surfaces as of local or extended reaction was found to be significant for surfaces consisting of multiple layers, specifically when one of the layers is air. For multilayers of solid materials with an air-cavity, this was most significant around their mass-air-mass resonance frequencies. Accounting for interference effects made significant changes in the predicted values of all parameters. Modeling phase change on reflection, on the other hand, was found to be relatively much less significant.

Overview of geometrical room acoustic modeling techniques

“…Yousefzadeh and Hodgson compared predictions of energy-and pressurebased coefficients as well, especially from the viewpoint of local and extended reactions. 135 Their main conclusion was that a pressure-based model with extended reaction is needed if the space under study includes multi-layered surfaces.…”

Recent advances in building acoustics: An overview of prediction methods and their applications

“…In the area of beam tracing method, some recent works [31][32][33] focused on the influence of boundary conditions on the prediction results. In the work of Siltanen et al [ 34], they presented a way to introduce incoherent reflections in a beam tracer algorithm.…”

Ray-tracing semiclassical (RTS) low frequency acoustic modeling validated for local and extended reaction boundaries

“…In such case the extended reaction assumption is preciser and improves the theoretical and experimental agreement of sound pressure level predictions [26]. Moreover, the significance of introducing extended reaction boundaries into computer models has been demonstrated -using phased beam tracing, the influence on the steady state sound pressure level in frequency bands was shown by Hodgson and Wareing [27] and on several acoustic parameters (strength, reverberation time and rapid speech transmission index) by Yousefzadeh and Hodgson [28]. Recently, Yasuda et al [29] showed by wave-based modeling that the extended reaction alters the response in particular at low frequencies, which is also the frequency range of our interest.…”