The near-field of spinning sources: Why source identification is hard

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Abstract

An asymptotic analysis is presented for the near field of spinning sources, based on a transformation into cylindrical coordinates centred on a line at a fixed radius from the source axis. This transforms the circular source into an equivalent finite length line source with a source distribution made up of `modes' given as Chebyshev polynomials of the second kind. These `modes' play a role like that of modes in ducts and the analysis shows that their acoustic field propagates or decays depending on whether the mode order is less than, or greater than, wavenumber respectively, similar to the cut-on/cut-off behavior of duct modes. The analysis is used to examine the problem of identifying a source from field measurements. This has a wide range of applications and is recognized to be (very) ill-conditioned. Using the information supplied by the analysis of the source near field, the reasons for this ill-conditioning are explained.
Original languageEnglish
Pages040004-040004-11
DOIs
Publication statusPublished - 2010
Event159th Meeting of the Acoustical Society of America/NOISE-CON 2010 - Baltimore, USA United States
Duration: 19 Apr 201023 Apr 2010

Conference

Conference159th Meeting of the Acoustical Society of America/NOISE-CON 2010
CountryUSA United States
CityBaltimore
Period19/04/1023/04/10

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  • Cite this

    Carley, M. (2010). The near-field of spinning sources: Why source identification is hard. 040004-040004-11. Paper presented at 159th Meeting of the Acoustical Society of America/NOISE-CON 2010, Baltimore, USA United States. https://doi.org/10.1121/1.3431358