Time-domain solutions of the linearized Euler equations have proved to be an attractive approach to study outdoor sound propagation. Indeed, it has been shown that the main phenomoena that influence acoustic propagation can be accurately taken into account. In the context of transportation noise, acoustic sources are complex because they are moving and they are generally not compact. Equivalent sources which are in most of the cases point sources are often used to simplify the problem and heuristic methods have been proposed to handle acoustic propagation. Time-domain methods can be used to validate these models. However point sources in arbitrary motion are difficult to account for in these approaches. Distributed volume sources can be used instead. This paper deals with modeling of sources in motion in time-domain solvers. Influence of the spatial support of the source on the acoustic field is also investigated. Results obtained for a fixed source are summarized and exemple of a gaussian spatial support is presented. The case of a harmonic source moving at a constant speed is investigated. Directivity of a non-compact source is shown to be dramatically different to the one of a monopole. Simulations of a moving source above an impedance ground surface in a three-dimensional geometry are then presented.
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