Numerical Development of a Low Height Acoustic Barrier for Railway Noise Mitigation

Abstract

AbstractAlthough railway system is the most sustainable mode of transport, with the lowest energy consumption, the noise induced by rail traffic in urban regions is a significant drawback. Mitigation of railway noise can be performed by different solutions, namely by the implementation of acoustic barriers. Although they offer a significant reduction in noise levels, their height makes people feel enclosed. Therefore, in the case of the railway infrastructure, the solution to the problem may lie in the use of barriers with a lower height placed close to the track. The purpose of this paper is to illustrate the development of a barrier solution to be used in a railway context through numerical modelling with Boundary Elements Method. The solutions developed were placed close to the track and have a low height (approximately 0.8m above the rail head). The geometry was defined, as mentioned, using 2D BEM from the numerical simulation of a sound wave. Thus, it was possible to match the inner face of the barrier with the geometry of the wavefront, favouring the normal reflection of the sound waves and directing the energy back to the track to take advantage of the acoustic properties of the ballast. The addition of a porous granular material on the inner face of the barrier, through the numerical simulation of an equivalent fluid and corresponding coupling to the acoustic medium, allows the control of reflections between the vehicle body and the barrier, increasing its acoustic efficiency. The solutions presented show great efficiency in terms of energy loss in the receivers with and without the barrier, i.e., in terms of Insertion Loss, the solutions presented give losses greater than 10 dB over a wide range of frequencies. In the case of the barrier with the presence of porous granular material, the barrier efficiency is even more remarkable with an increase of at least 5 dB compared to the solution without porous granular material.KeywordsFirst keywordSecond keywordAnother keyword