Physically-based numerical sound propagation modeling in rooms with non-flat walls.

Nowadays, accurate sound propagation modeling is one of the main research axes in room acoustics. Many numerical methods exist, each with their own benefits. Nevertheless, compromises in terms of accuracy, size of the studied domain or frequency range of calculation must be made even for the most advanced models. The objective of this work is to develop a numerical method modeling the sound propagation in an enclosed space (e.g. an industrial workplace) and taking accurately into account the sound scattering influence of the geometrical irregularities of the walls (cavities, beams, windows, etc.). The method developed in this paper is based on the adaptive rectangular decomposition method (ARD) with an improved consideration of the boundary conditions. First, this study describes a way to improve the calculation and to reduce the error induced by perfectly matched layers (PML) used to absorb sound waves at the room boundaries. Then, it details how to implement frequency-dependent reflection at the boundaries using digital impedance filters (DIF) and boundary conditions based on the finite-difference time-domain method (FDTD). Finally, the model was validated, first by comparison with calculations using the Kobayashi Potential method and with measurements, both carried out to obtain the acoustic pressure above a complex surface constituted by rectangular cavities in free field conditions. Then, it was validated by comparison with the image source method and measurements in a real room.