Abstract
In most previous studies of sound radiation from railway rails, the rail has been regarded as located in free space, disregarding the influence of the ground. However, in order to predict the noise from the rail more precisely, the effect of the ground should be included in rolling noise predictions. In this study, the rail noise is investigated by means of a wavenumber domain numerical method, including the presence of the ground. For rails attached to a rigid ground or located at a certain distance above it, the influence of the ground is examined in terms of the radiation ratio and longitudinal directivity. From the prediction of radiated power, it is found that the vertical and lateral bending waves of the rail radiate most of the noise for the corresponding direction. Hence, a simplified calculation is proposed that only includes these waves, instead of a full three-dimensional analysis. An absorptive ground is also modelled by applying impedance boundary conditions at the ground surface to investigate the influence of the ground on the rail noise. Finally, for the vertical and lateral bending waves in the rail, the cross-sectional directivity of the noise is predicted for various surface impedances of the ground. It is found that the simplified calculation proposed in this study is valid for the prediction of noise from the rail. Also the presence of the ground and its impedance condition have considerable effects on the level and directivity patterns of the noise radiated from the rail.
Highlights
Rolling noise is known to be one of the main sources of environmental noise from railways, for conventional train speeds
Nilsson et al [7] have extended this wavenumber domain approach by combining the waveguide finite element method (WFE) with waveguide boundary elements (WBEs) and used this combined method to investigate the sound radiation from an embedded rail as well as a rail in free space
The noise radiated by a rail in the presence of a ground was investigated by means of the wavenumber domain finite and boundary elements method
Summary
Rolling noise is known to be one of the main sources of environmental noise from railways, for conventional train speeds. Nilsson et al [7] have extended this wavenumber domain approach by combining the WFEs with waveguide boundary elements (WBEs) and used this combined method to investigate the sound radiation from an embedded rail as well as a rail in free space. This method allows a three-dimensional analysis of the sound radiation from an infinite rail. Zhang et al [18] have investigated the effect of the ground on the radiation ratio of a rail by using a 2D boundary element method; they introduced corrections into the model to consider the wavenumbers of the propagating waves in the rail.
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