The effects of rail support stiffness on railway rolling noise

Rolling noise from trains is radiated by both wheel and track vibrations, the track being dominant in many cases. The stiffness of the rail fastener system, especially the elastomeric rail pad usually inserted between the rails and the sleepers, has a significant influence on the noise emitted by the track. Railways are increasingly using softer pads to reduce potential damage to sleepers and ballast. Softer pads decouple the rail from the sleeper. This reduces the noise from the sleeper but also reduces the decay of vibration with distance along the rail and hence leads to an increase of the noise radiated by the rail. The paper describes experimental and theoretical work to investigate the influence of pad stiffness on the dynamic and acoustic behavior of track. The vibrational behavior has been measured on a dedicated 36-m section of railway track, with different types of rail pad installed. The results are compared with predictions using theoretical models of the track behavior. This allows the effective pad stiffness and damping to be determined, laboratory measurements also being available for comparison. The attenuation of vertical and lateral vibration along the track is measured in order to estimate the effect on radiated noise.