Rail and wheel roughness - implications for noise ... - ARCHIVE: Defra

AEATR-PC&E-2003-002
Appendix C
Analysis of Pass-by Noise
Trains often comprise a number of different types of vehicle. This can create a problem when
trying to measure the amount of noise produced by a particular type of vehicle that can only
run as part of a train. The problem becomes particularly difficult when the train has a mixture
of wheels with cast iron tread brakes and disc brakes. An example of a time history for an
HST is shown in Figure C-1.
64 ms LAeq (dB)
105
100
95
90
85
80
75
70
65
60
Noisy Wheels
Power car
Power car
Trailer cars
0 2 4 6 8 10
Time (secs)
Figure C-1 A typical pass-by time history for an HST travelling at 155 km/h, measured
7.9 m from track centre line.
In this figure, the importance of the cast iron tread brakes on the power cars can be seen.
Furthermore, the effect of some noisy wheels can also be seen. The reason these wheels are
noisy is likely to be the result of tread damage.
In the early 1970s Peters developed a way of predicting the time-histories of passing trains
(C1). This method treats each wheel as a simple dipole and by defining the sound power
radiated by each wheel it is possible to predict the time-history. Clearly, using the same
approach it should be possible to predict the sound powers of the sources given a measured
time history. In practice, because the noise at any moment in time is a combination of the
noise from all the wheels in the train, there are some limitations to this approach. The main
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