Experimental study of noise mitigation measures on a slab track

Abstract Slab track is generally noisier than conventional ballasted track, so noise control measures that can be applied to a slab track are of great importance. Several noise control treatments have been studied under controlled conditions through experiments on a 1:5 scale model slab track with and without the presence of a train body. These treatments consist of absorptive rubber mats applied to the surface of the slab and a low noise barrier introduced close to the track. The noise reduction is evaluated experimentally by using a reciprocal method and compared with the results of numerical simulations. The insertion loss spectra of these treatments have been combined with predicted train pass-by spectra to determine the potential overall noise reductions. It has been found that the absorptive treatment alone has only a small effect on the radiated noise from the track. This is increased by the presence of the train body leading to a reduction of up to 2–3 dB at a standard receiver height of 1.2 m, which suggests that the absorptive layer controls reflections between the car body and the track. All the treatments considered have a greater effect on the noise radiated by the lateral vibration of the rail than on that from the vertical vibration. Their effectiveness mostly increases, by between roughly 0.5 and 1.5 dB, as the train speed is increased from 80 to 300 km/h. As expected, the noise barrier is more effective at lower receiver positions than at higher ones but its effectiveness is reduced by 1–2 dB by the presence of the train body. However, in combination with the absorptive treatment, its effectiveness increases when the train body is present. This shows the importance of including of the presence of the train body in evaluating the effects of acoustic treatments in the track.