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Signal processing of aircraft flyover noiseA detailed analysis of signal processing concerns for measuring aircraft flyover noise is presented. Development of a de-Dopplerization scheme for both corrected time history and spectral data is discussed along with an analysis of motion effects on measured spectra. A computer code was written to implement the de-Dopplerization scheme. Input to the code is the aircraft position data and the pressure time histories. To facilitate ensemble averaging, a level uniform flyover is considered in the study, but the code can accept more general flight profiles. The effects of spectral smearing and its removal are discussed. Using test data acquired from an XV-15 tilt-rotor flyover, comparisons are made between the measured and corrected spectra. Frequency shifts are accurately accounted for by the de-Dopplerization procedure. It is shown that by correcting for spherical spreading and Doppler amplitude, along with frequency, can give some idea about noise source directivity. The analysis indicated that smearing increases with frequency and is more severe on approach than recession.
Document ID
19930046469
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kelly, J. J.
(Lockheed Engineering & Sciences Co. Hampton, VA, United States)
Date Acquired
August 16, 2013
Publication Date
January 22, 1993
Publication Information
Publication: Journal of Sound and Vibration
Volume: 160
Issue: 3
ISSN: 0022-460X
Subject Category
Acoustics
Accession Number
93A30466
Funding Number(s)
CONTRACT_GRANT: NAS1-19000
Distribution Limits
Public
Copyright
Other

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