LOWNOISEPAD: Low-cost noise control by optimized rail pad: Feasibility study on the use of rail pad as noise mitigation measure

When aiming to minimize track noise, there is a significant conflict of aims that must be considered. Tracks with stiff rail pads are generally less noisy than ones with soft rail pads. Stiff rail pads, however, can decrease the long-term quality of the track. In order to achieve an optimum, beside stiffness also rail pad damping at relevant frequencies must be considered. The International Union of Railways (UIC) works with its members to better understand the noise-generation and rail pad effects. The LOWNOISEPAD project brings together the European railway community in an effort to find an optimal rail pad for both noise and track quality issues and for the different situations encountered in 12 European railway networks. Besides acoustic rail roughness, the stiffness and damping properties of rail fastening systems such as rail pads have a considerable influence on rail noise. In practice, rail pad design is always a compromise between track engineers' demand for flexibility and acoustic engineers' expectations for sufficiently high Track Decay Rate. The paper describes the measurements undertaken in the project, shows first conclusions as well as a software tool that allows determining noise levels after installing rail pads with given stiffness and damping properties.