An investigation into inconsistencies between theoretical predictions and microphone array measurements of railway rolling noise


Kitagawa, Toshiki (2007) An investigation into inconsistencies between theoretical predictions and microphone array measurements of railway rolling noise. University of Southampton, Institute of Sound and Vibration Research, Doctoral Thesis , 205pp.

Download

[img] PDF
Download (3600Kb)

Description/Abstract

Theoretical models, such as TWINS, and microphone array measurements have been
widely used to gain better understanding of rolling noise. However, the array
measurements are often inconsistent with the TWINS predictions and give less
prominence to the rail than the theoretical models. The objectives of this thesis are to
make validation work of the TWINS model for Japanese railway lines, and to explore the
reason why the microphone array gives a correct estimate of sound power radiated by the
rail.
A comparison in terms of noise and rail vibration has been carried out for six wheel/rail
conditions of Japanese railways. The TWINS predictions show good agreement with the
measurements. After confirming the applicability of the TWINS model, the effects of
wheel load on noise and rail vibration are investigated, and the predictions show similar
trends to the measurements. The acoustic properties of a rail as measured with a
microphone array have been investigated through simulations and field tests. In the
simulation the rail is modelled as an array of multiple sources. Results are given for two
situations: (a) the multiple sources are incoherent, which is assumed in determining
sound power from a microphone array, (b) the sources are coherent, which is more
representative of the rail radiation. It is found that the microphone array cannot detect a
large part of the noise generated by the rail in the frequency range where free wave
propagation occurs. Sound measurements were carried out to validate the radiation model
of the rail by using a shaker excitation of a track. It is found that the noise is radiated
from the rail at an angle to the normal when free wave propagation occurs in the rail, and
that the predictions based on coherent sources show good agreement with the
measurements. Sound measurements for a moving train were also performed with a
microphone array. It is shown that the microphone array misses a large part of noise
generated by the rail, when directed normal to the rail. This leads to an underestimation
of the rail component of the noise in the array measurements.

Item Type: Thesis (Doctoral)
Subjects: T Technology > TF Railroad engineering and operation
Q Science > QC Physics
Divisions: University Structure - Pre August 2011 > Institute of Sound and Vibration Research > Dynamics
ePrint ID: 51264
Date Deposited: 16 May 2008
Last Modified: 27 Mar 2014 18:34
URI: http://eprints.soton.ac.uk/id/eprint/51264

Actions (login required)

View Item View Item

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics