Influence of Vertical Fastener Stiffness on Rail Sound Power Characteristics: Numerical Study and Field Measurement

Abstract

The aim of this paper is to investigate the influence of vertical fastener stiffness on the sound power characteristics of rail rolling noise. The rail mobility is obtained by using the Timoshenko-beam track model and the spectral element method. The decay rate is obtained by using the periodic track model and the spectral transfer matrix method. Then, the simulation results of the rail mobility and the decay rate are used to calculate the sound power level of the rail subjected to a harmonic point excitation. Furthermore, the influence of vertical fastener stiffness on the rail sound power level is investigated. Finally, field measurements of the rail accelerance and the decay rate are performed to verify the accuracy of models and calculation methods. The results show that the sound power level of the rail subjected to a harmonic point excitation increases with the increase of the frequency and peaks at the center frequency of 800 Hz. When the vertical fastener stiffness decreases from 50 kN/mm, the rail sound power level below the center frequency of 200 Hz gets increased. The increase of the sound power level is most significant at the center frequency which is close to the decreased vertical rail resonance frequency, because in the corresponding one-third octave band the rail mobility amplitude increases significantly while the decay rate decreases considerably. The simulations of the rail accelerance and the decay rate both coincide well with the measurements.