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A study of helicopter interior noise reductionThe interior noise levels of existing helicopters are discussed along with an ongoing experimental program directed towards reducing these levels. Results of several noise and vibration measurements on Langley Research Center's Civil Helicopter Research Aircraft are presented, including measurements taken before and after installation of an acoustically-treated cabin. The predominant noise source in this helicopter is the first stage planetary gear-clash in the main gear box, both before and after installation of the acoustically treated cabin. Noise reductions of up to 20 db in some octave bands may be required in order to obtain interior noise levels comparable to commercial jet transports.
Document ID
19750015484
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Howlett, J. T. (NASA Langley Research Center Hampton, VA, United States)
Clevenson, S. A. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 3, 2013
Publication Date
May 1, 1975
Subject Category
Aircraft Design, Testing And Performance
Report/Patent Number
L-10076
NASA-TM-X-72655
Report Number: L-10076
Report Number: NASA-TM-X-72655
Meeting Information
Meeting: Ann. Natl. Forum of the Amer. Helicopter Soc
Start Date: May 1, 1975
Accession Number
75N23556
Funding Number(s)
PROJECT: RTOP 504-09-21-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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