Diffuse sound field modelling in streets by the transport theory

Inter.Noise 2004, 33rd International Congress and Exposition on Noise Control Engineering, PRAGUE, TCHÈQUE, RÉPUBLIQUE, 22-/08/2004 - 25/08/2004In cities, noise is often described as one of the most annoying pollution. Thus, many studies concerning the sound propagation in urban areas have carried out. More particularly, a recent work has shown that it was possible to use the sound particles concept to model the sound propagation in rectangular streets. One of the particularities of this model is to take into accound every reflection law of a building façade. The mathematical development is based on a transport equation, similar to the free molecular flow equation. Boundary conditions have been considered by local flux equations including the reflection laws of the façades. In the case of a narrow street, the transport equation can be reformulated in an diffusion equation, whose fundamental parameter is defined as the diffusion coefficient and characterizes the propagation medium. The model has been validated for perfectly reflecting façades, with identical and symmetrical reflection laws (like Lambert's law) on both sides of the street. In this paper, we propose to generalize the model to include different reflection laws on both sides of the street. In order to validate this new development, Monte Carlo simulations have been realized for different sizes of the street and several reflection laws. Those simulations are based on the propagation of sound particles in a rectangular including the façade effects. Finally, comparisons show that the model and simulations are quite in agreement