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Leading edge serrations which reduce the noise of low-speed rotorsAcoustic effects of serrated brass strips attached near the leading edges of two different size rotors were investigated. The two bladed rotors were tested in hover. Rotor rotational speed, blade angle, serration shape, and serration position were varied. The serrations were more effective as noise suppressors at rotor tip speeds less than 135 m/sec (444 ft/sec) than at higher speeds. high frequency noise was reduced but the low frequency rotational noise was little affected. Noise reductions from 4 to 8 db overall sound pressure level and 3 to 17 db in the upper octave bands were achieved on the 1.52 m (5.0 ft) diameter rotor. Noise reductions up to 4 db overall sound pressure level were measured for the 2.59 m (8.5 ft) diameter rotor at some conditions.
Document ID
19730019166
Acquisition Source
Legacy CDMS
Document Type
Other - NASA Technical Note (TN)
Authors
Soderman, P. T.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 2, 2013
Publication Date
August 1, 1973
Subject Category
Aircraft
Report/Patent Number
NASA-TN-D-7371
A-4074
Accession Number
73N27898
Funding Number(s)
PROJECT: RTOP 136-13-01-08-21
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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