Application de la méthode TLM à la modélisation de la propagation acoustique en milieu urbain

Abstract : Noise accounts for major societal matter, especially in urban and peri-urban areas where noise sources arising from road traffic are numerous and varied. Based on energetic and geometric models and initially developed for slightly built open-spaces applications, current acoustic prediction softwares are limited for urban and peri-urban areas acoustic prediction (various built and obstacles, moving real noise sources with time varying running speed...). The thesis work has consisted in putting forward a time-domain numerical domain for modelling the sound propagation in urban area. Among possible methods, the TLM ("Transmission Line Modelling") method constitute a original approach as it allows to account for complex propagation medium integrating most of physical phenomena brought into play during long range sound propagation (edge diffraction, reflection, steady-state phenomena, geometrical divergence, atmospheric attenuation, micrometeorological effects). However, the bibliographical study has given rise to two main limitations of the method to fully respond to our problematic: realistic boundaries conditions implementation and infinite propagation medium modelling. A generic TLM model has been developed and allows to perform simulations in two and in three dimensions by combining the whole phenomena influencing sound propagation in urban areas. An impedance boundary condition implementation is also proposed. The method consists in approximating the impedance as a sum of first-order linear systems. In addition, the use of a recursive convolution method enables to limit the computational cost of the boundary sound pressure calculation. Many simulations of sound propagation over manifold kinds of absorbing grounds have been performed and successfully compared with analytical solutions. Concerning the modeling of an infinite propagation medium, an anisotropic absorbing layers formulation for limiting the computational domain has also been derived. Finally, a few realistic urban applications (acoustic barriers, vegetalized frontages and flat roofs) have been proposed.
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Gwenaël Guillaume. Application de la méthode TLM à la modélisation de la propagation acoustique en milieu urbain. Acoustique [physics.class-ph]. Université du Maine, 2009. Français. ⟨tel-00793252⟩

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