An investigation into the effects of modelling assumptions on sound power radiated from a high-speed train wheelset

In predicting rolling noise from a railway wheelset, some assumptions are usually required to make the calculations less complicated and more efficient. In this study, the effects of some modelling assumptions on the prediction of sound power radiated from a high-speed train wheelset are investigated by using the finite element and boundary element methods. Use is made of the axi-symmetry of the wheelset to allow the solution to be obtained in terms of a Fourier series in the circumferential direction. Compared with a moving-wheel formulation, the moving-roughness approach is shown to be sufficient provided that the wheelset receptance takes into account the effects of rotation and the rail receptance accounts for the effect of the moving load. Wheel/rail coupling should take account of lateral as well as vertical forces; neglect of the lateral interaction may result in significant overestimates of the contribution of the axial modes of the wheelset, and thus the overall wheelset radiated noise. If the rotation of the wheelset is not considered, its radiated noise may be underestimated by up to 3 dB at frequencies above 2000 Hz. If the wheelset suspension is not included, the overall sound power would be overestimated at frequencies below 2000 Hz. Compared with symmetric excitation of the wheelset, assuming incoherent excitations for the left and right wheel/rail contacts will significantly affect the radiated noise in the frequency range below 2000 Hz but has negligible effect on the important region above 2000 Hz. Finally, the contribution from the axle is shown to be significant below 1000 Hz. In terms of overall A-weighted level, the effect of the lateral wheel/rail interaction, the rotation of the wheelset and the inclusion of bearings and axleboxes should not be neglected