Effect of ground conditions and microphone position on railway noise measurement results

Thompson, David J., Zhang, Xianying and Squicciarini, Giacomo (2021) Effect of ground conditions and microphone position on railway noise measurement results. In, Degrande, Geert (ed.) Noise and Vibration Mitigation for Rail Transportation Systems : Proceedings of the 13th International Workshop on Railway Noise, 16-20 September 2019, Ghent, Belgium. (Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 150) Springer Cham, pp. 680-687. (doi:10.1007/978-3-030-70289-2_75).

Abstract

According to ISO 3095, railway pass-by noise should be measured at 7.5 m from the track and at 1.2 m or 3.5 m above the rail head or at 25 m from the track and 3.5 m height. The level of the ground surface should be between 0 m and –2 m relative to the top of the rail. The level of the ground and nature of the ground surface can affect the spectral content of the measured sound. In this paper the TWINS model is used for a range of situations to illustrate the effect of ground height and equivalent flow resistivity on the sound pressure spectrum. The location of the ground dip is shown to depend on the ground properties. Measurement results support these results. For the particular cases illustrated it is shown that the differences between the overall A-weighted noise levels at 7.5 m and 25 m can vary between 4.6 and 7.4 dB for the cases considered. Moreover, the noise level differences between different track types can also vary by several dB. In particular, the level differences between two ballasted tracks and a slab track are found to vary in a range of about ± 2 dB.

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Contributors

Author: David J. Thompson

Author: Giacomo Squicciarini

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