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

AEATR-PC&E-2003-002
limitation is that the combined length of the 'quiet' vehicles is less than 1.5 times the distance
from the measurement point to the track. It can be seen that this is not a problem in Figure C-
1 as the individual trailer cars are 23 metres long.
When a vehicle is noisier than the adjacent vehicles the situation is much simpler. This is
because louder noises will dominate quieter noises when combined on the decibel scale and is
illustrated in Figure C-1 by the peak caused by 'Noisy' wheels.
Assuming that all the wheels on the power cars are the same and, except for the 'noisy’
wheels, all wheels on the trailer cars are the same, the average sound powers for the power car
wheels, the trailer car wheels and the 'noisy' wheels can be calculated. Figure C-2 shows the
predicted train time history using these calculated average sound powers.
64 ms LAeq (dB)
105
100
95
90
85
80
75
70
65
60
Measured
Train Predicted
Trailer Cars Predicted
0 2 4 6 8 10
Time (secs)
Figure C-2 The measured and predicted pass-by time histories for an HST
Figure C-2 also includes the time history for the trailer cars without the 'noisy' wheel. Using
this time history for the trailer cars it is possible to calculate the pass-by L Aeq , SEL, TEL and
L Amax .
This approach has the advantage that it produces a result that uses the maximum amount of
available data and so improves the statistical reliability of the result.
Reference
C1
S Peters, 'The prediction of railway noise profiles'; Journal of Sound and Vibration,
Volume 32, No. 1, pages 87-99, 1974
AEA Technology 55