Effects of railway ballast on the sound radiation from the sleepers

Zhang, Xianying, Thompson, David and Squicciarini, Giacomo (2015) Effects of railway ballast on the sound radiation from the sleepers. 10th European Congress and Exposition on Noise Control Engineering, Euronoise 2015, , Maastricht, Netherlands. 01 - 03 Jun 2015. pp. 2037-2042 .

Abstract

Railway ballast is an important component in the railway system. It is a layer of stones located below and around the sleepers; it supports the track vertically and provides lateral stability. The gaps between the stones make it behave acoustically as a porous material, absorbing noise to some extent. In addition, ballast can itself vibrate and reradiate noise during train pass-by. It is not clear, however, to what extent the ballast contributes to the noise and how much its mechanical and acoustical properties modify the radiation of the sleeper and the rail. This paper focuses on quantifying the influence that ballast has on noise, particularly on the sleeper radiation. A one-fifth scale model of the track is used to conduct acoustic and vibration measurements on ballast. Two different scaling factors (1:√5 and 1:5) are adopted for the stone sizes to reproduce the acoustic properties of the ballast. It is shown that although a scale factor of 1:√5 gives a better scaling of the acoustic properties, the stones scaled at 1:5 also give acceptable results. The effects of the ballast on the noise radiation from a scaled concrete sleeper are obtained experimentally with the ballast located either on a rigid foundation or on a flexible wooden base. The ballast vibration in these configurations has been obtained by using a scanning laser vibrometer. Finally, the effects of ballast vibration on the sleeper radiation are evaluated by means of a prediction based on the Rayleigh integral.

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Contributors

Author: David Thompson

Author: Giacomo Squicciarini

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