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Importance of engine as a source of helicopter external noiseA turboshaft engine's importance as a source of helicopter external noise is presently evaluated experimentally and analytically on the basis of test data from an MD500E helicopter, with and without engine muffler, during level flyovers and climbing flight. A strong engine noise component is noted for helicopter positions nearly overhead and beyond observed position, especially in the 200-1000 Hz range; its strong rearward directivity suggests the noise source to be the broadband exhaust or combustion noise radiated from the exhaust duct. The engine muffler furnished estimated perceived noise level reductions of 2-3 dB for the centerline.
Document ID
19890046400
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Janakiram, R. D.
(McDonnell-Douglas Helicopter Co. Mesa, AZ, United States)
Smith, M. J.
(McDonnell-Douglas Helicopter Co. Mesa, AZ, United States)
Tadghighi, H.
(McDonnell Douglas Helicopter Co. Mesa, AZ, United States)
Date Acquired
August 14, 2013
Publication Date
April 1, 1989
Subject Category
Aircraft Design, Testing And Performance
Report/Patent Number
AIAA PAPER 89-1147
Accession Number
89A33771
Funding Number(s)
CONTRACT_GRANT: NAS1-17145
Distribution Limits
Public
Copyright
Other

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