The horizontal directivity of noise radiated by a rail and implications for use of microphone arrays
Kitagawa, Toshiki and Thompson, David J. (2010) The horizontal directivity of noise radiated by a rail and implications for use of microphone arrays. Journal of Sound and Vibration, 329, (2), 202-220. (doi:10.1016/j.jsv.2009.09.002).
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Structural waves propagating along a railway rail form an extended source of sound radiation. Using an equivalent source model the distribution of this sound in a horizontal plane is investigated and shown to consist mainly of sound propagation at a particular angle to the normal. This direction is determined by the ratio of the wavenumbers in the rail and in air. Due to the extended nature of the rail as a source, the spatial distribution of the sound field in the direction along the track does not lend itself to the use of a simple directivity factor. The consequences for the measurement of noise from the rail using a microphone array are then explored. It is shown that a microphone array focussed normal to the rail does not detect most of the sound radiated by the rail. By turning the focus angle, the sound detected becomes a maximum when this angle corresponds to the angle of propagation of the sound radiation. Measurements on a test track using artificial excitation and measurements during the passage of a train confirm these conclusions
|Subjects:||Q Science > QC Physics|
|Divisions:||University Structure - Pre August 2011 > Institute of Sound and Vibration Research > Dynamics
|Date Deposited:||29 Apr 2010 13:07|
|Last Modified:||01 Jun 2011 01:02|
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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