The sound radiation of a railway rail fitted with acoustic shielding

The most important source of environmental noise from railways is rolling noise; the component of noise radiated by the rail is often the highest, and dominates the important mid-frequency region between 400 and 2000 Hz. One measure to reduce the noise from the rail at source is a rail damper which increases the track decay rate. Several such products are now available. This paper investigates an alternative which is a shield fitted around the lower part of the rail. A layer of porous material is also included to increase the absorption inside the shield. The sound radiation of this concept is investigated theoretically by using a 2.5D finite element / boundary element approach. The overall noise reduction that can be achieved by this measure when applied to the railway track is determined by combining the numerical results with estimates of rolling noise from the TWINS model. For a freight train on a track with soft rail pads an overall noise reduction of 2.5 dB(A) is predicted whereas for a track with stiff rail pads the reduction is only 1 dB(A)