Size-adaptive spherical receptor acceleration method for acoustical ray tracing

Abstract

Randomized ray tracing in room acoustics can be used to compute echograms, but the results computed at the receptor are affected by statistical errors [1]. To decrease these statistical errors, the usual solution is to increase the number of rays, but this also increases the computation time. Another solution is to increase the receptor size, but this lowers the spatial resolution of the computed sound field, which is particularly important for the early part of the echogram. In order to decrease the computation time and keep a sufficient resolution, the method proposed in this paper is based on a progressive modification of the receptor size (spherical type) as long as the ray's travel grows. At the same time, the number of rays into the room can be decreased as the sound ray lengths increase while keeping the statistical errors more or less constant. The consequence is that the sound field spatial resolution evolves from “precise” at the beginning of the echogram to “rough” at its end. The first applications of this new method show a significant gain of CPU time. [Broad spectrum diffusion model for room acoustics ray-tracing algorithms, J. J. Embrechts, Jnl. Acoust. Soc. Am. 107(4) 2068-2081 (2000)].

Accounting for the effect of diffuse reflections and fittings within street canyons, on the sound propagation predicted by ray tracing codes

“…This size of receivers is in agreement with previous works, which preconize receivers of radius between 0.25 and 1 m [28,29]. Then, considering one million of initial particles, with a time step of Dt = 0.01 s, and a duration of simulation of T = 1 s, is sufficient to reproduce the direct field and the first reflections.…”