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A noise study of the A-6 airplane and techniques for reducing its aural detection distanceA study was undertaken to determine the noise reduction potential of the A-6 airplane in order to reduce its aural detection distance. Static and flyby noise measurements were taken to document the basic airplane signature. The low-frequency noise which is generally most critical for aural detection was found to be broad-band in nature from this airplane, and its source is the turbojet engine exhaust. High-frequency compressor noise, which is characteristic of turbojet powerplants, and which is prominent at close range for this airplane, has no measurable effect on aural detection distance. The use of fluted-engine exhaust nozzles to change the far-field noise spectra is suggested as a possible means for reducing the aural detection distances. Detection distances associated with eight-lobe and four-lobe nozzles are estimated for a 1,000-foot altitude and grassy terrain to decrease from 4 miles to about 3 miles, and from 3 miles to about 2 miles for a 300-foot altitude and grassy terrain.
Document ID
19750010164
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Hilton, D. A. (NASA Langley Research Center Hampton, VA, United States)
Connor, A. B. (NASA Langley Research Center Hampton, VA, United States)
Hubbard, H. H. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 3, 2013
Publication Date
April 1, 1975
Subject Category
Aircraft Propulsion And Power
Report/Patent Number
NASA-TM-X-72643
Accession Number
75N18236
Funding Number(s)
PROJECT: RTOP 505-03-12-05
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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