The Influence of the Vehicle Body on the Sound Radiation from the Rail

Numerical models and vibro-acoustic measurements are used to assess the effect of reflections from the underside of a railway vehicle on the sound radiation from the rail. A 2D boundary element model is used in which the rail vibrates uniformly in either vertical or lateral directions; various different shapes of vehicle body are introduced into the model. Measurements are performed on a 1:5 scale model and on a full-size track with and without a metro vehicle. The presence of the vehicle primarily affects the sound pressure from the vertical vibration of the rail, with negligible effect for the lateral vibration. The vehicle body reflects the sound back down towards the track where it is partly absorbed by the ballast, reducing the sound power. Nevertheless, the sound pressure at the trackside is increased by 0–5 dB and in some frequency bands by up to 9 dB. Finally, it is shown that the sound radiation in the presence of the vehicle can be approximated reasonably well with simple line source formulae.