Towards time-domain modelling of wheel/rail noise: Effect of the dynamic track model

Journal article, 2024

Transient events in railway rolling noise, such as the characteristic impulsive noise at switches and crossings, can significantlycontribute to the perceived annoyance, despite being difficult to detect in the standard frequency-domain methods to analyserolling noise. Studying these transient effects and their perception requires predicting the noise in the time domain. Whileseveral time-domain approaches exist for predicting the dynamic interaction of wheel and rail, predicting the associated rollingnoise with adequate accuracy is computationally costly. The lack of a model for transient noise and the need for studying itsperception was recently identified. Aiming for a comprehensive time-domain radiation model that includes the wheel andtrack contributions to rolling noise, this work focuses on the track radiation. The modelling approach taken here is based on a2.5D formulation for the acoustic radiation and moving Green’s functions in the air. The computational cost, which lies mainlyin the 2.5D BE calculations, is addressed by pre-calculating acoustic transfer functions. These transfer functions can becombined with different dynamic track models. Different dynamic track models in turn affect radiated soundfield in differentways. Here, the soundfields produced by six different track models are compared, including different support types andanalytical and numerical rail models. Several descriptors of the soundfield are analysed. In terms of the radiated sound powerand radiation efficiency, modelling the rail as a simple beam leads to similar results as elaborate numerical models up to about5 kHz. In terms of the track-side sound pressure, simple beam models can provide similar results only up to 2.5 kHz. Euler-Bernoulli (E-B) beams seem unfit for time-domain predictions of the radiated noise as they over-estimate the bending wavespeed at high frequencies. The results also show that the standard track decay rate (TDR) and the decay of acoustic soundpressure along the track are comparable.