Noise radiated by ground surface vibrations due to passing trains.

Noise radiated by passing trains is usually modelled without considering the radiation of the soil free surface. Models such as TWINS will only consider the acoustic radiation of the different trains and tracks components as a sum of individual acoustic sources defined by their power and directivity expressed in the frequency domain and used as elementary sources in acoustic propagation models. The vibroacoustic model Mefissto, developed at CSTB, can be used to compute the propagation of vibrations from a train to a building as well as the ground borne noise inside lodgings. To compute the noise radiated by the ground free surface one will use the vibration field of a rectangular portion of the surface computed in 3D and evaluate its radiation in the air by means of the Rayleigh integral representation. The Rayleigh integral can be extended by using more complex Green functions, computed by the source image method allowing to consider the presence of one or two buildings. On site acoustic and vibration measurements have been made near a railway line. The calibrated soil model has been used to estimate the noise radiated by the ground which compared to the measured sound pressure levels has showed that the soil radiation is important below 160 Hz.