ENHANCED TRAIN-TRACK NOISE SEPARATION FROM PASS-BY MEASUREMENTS
Proceedings of the International Congress on Sound and Vibration
The accurate separation of noise contributions, of the train and the track, in a pass-by event has significant practical value: the identification of who should take action, or be accountable: the track manager; or the rolling stock operator, for a noise pollution event; and, to enable more targeted design of noise mitigation measures directed at the identified source. This paper extends an empirical train-track noise separation method, the so-called Vibro-acoustic Track Noise, VTN, method. This is achieved by replacing the rail radiation ratios and directivity factors, as inferred from beam-based analytical models, with more accurate results obtained from finite-element and boundary-element analysis. This accounts for the approximately infinite nature of the track in the longitudinal direction. Site-specific track characteristics, such as track component stiffness and rail cross-section profile, can be considered. The sleeper model has been enhanced from one based on a baffled plate for each sleeper to one which allows the radiation area to change with the frequency. The ground effect, in affecting noise during propagation, has also been quantified by field test and taken into account in the proposed approach. Test results from a week-long wayside noise and vibration test are reported. The results indicate that the overestimation of the track noise contribution, i.e. below 1.5 kHz, when applying the original VTN method, is significantly reduced by the proposed approach.
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