Simulation of room transmission functions using a triangular beam tracing computer model

The triangular beam method (TBM) combines the advantages of both the mirror image source method (MISM) and the ray tracing method (RTM). In combination with a wall diffusion model, it enables one to simulate within reasonable calculation times high time-resolution reflectograms in any complex geometrical shape. The so-obtained echograms have been further processed, in order to calculate steady-state room transmission functions. The conversion from time domain to frequency domain has not been accomplished by FFT, but by a more direct method, superimposing wavelengths on the calculated ray paths. The method is relatively fast and has been compared with boundary element (BEM) calculations, showing a very good agreement between both approaches. This direct method is especially useful for simulating room transmission functions in the medium frequency region, i.e. the transition zone between the low-frequency domain in which wave acoustics dominate and the high-frequency domain, regulated by geometrical acoustics.