Analyse numérique et expérimentale de la propagation acoustique extérieure : effets de sol en présence d'irrégularités de surface et méthodes temporelles

Abstract : In the context of prediction models improvement for outdoor sound propagation, this work focuses on the modelling of the effects of ground irregularities on sound propagation. Time-domain numerical methods are used: on one hand, the solving of the governing equations by finite difference schemes (FDTD method), and on the other hand, the transmission line matrix (TLM) method. Effective impedance is considered to model the effects of surface roughness. Two effective impedance models are studied: the first one takes into account the effects of a deterministic roughness formed by scatterers of constant geometry, the second one takes into account the mean effects of a random roughness defined by a roughness spectrum. This second model is validated experimentally by a measurements campaign carried out in a semi-anechoic chamber, above rough surfaces whose roughness profiles were precisely designed. The two effective impedance models are also validated by FDTD and TLM simulations. The possibility to use the effective impedances directly into the numerical methods is then shown, allowing the modelling of roughness effects without meshing the exact height profile of the ground surface. A measurements campaign of the impedance of different grounds is performed in order to assess the effects of space and seasonal variability of the impedance on the sound levels predictions. The results of this campaign are also used as realistic entry data for the TLM code, and the propagation above a heterogeneous ground showing spatially variable impedance is simulated.
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Olivier Faure. Analyse numérique et expérimentale de la propagation acoustique extérieure : effets de sol en présence d'irrégularités de surface et méthodes temporelles. Acoustique [physics.class-ph]. Ecole Centrale de Lyon, 2014. Français. ⟨tel-01132517⟩

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