Reduction of vibration emissions and secondary airborne noise with under-sleeper pads—effectiveness and experiences

Abstract

In the railway superstructure under-sleeper pads are primarily used for ballast protection and to improve the track quality. They increase the contact area between concrete sleepers and the top ballast layer, reduce the formation of hollowness beneath sleepers and lower superstructure settlements. But elastic under-sleeper pads can also represent a cost-effective way to reduce the transmission of vibration and structure-borne noise. To this effect the formation of a vibratory system is required. Both effects, improvement of the track quality and formation of a vibratory system, have an impact on the measured insertion loss which is discussed in this article. Derived from this result, the challenges of a computational prognosis of the vibration mitigation effect are described. In the light of experience gained in projects carried out with under-sleeper pads for vibration reduction, the achieved results are presented by means of examples.