Noise reduction is mostly limited to light helicopters whose noise signature is dominated by their tail rotors. It is primarily hardware oriented. Well known noise reduction techniques such as reduction of rotor speeds with an accompanying increase in solidity to maintain performance, engine noise reduction with the use of exhaust mufflers, and acoustic blanketing of transmission and engine compartment are used. The concept of blade phasing as a means of reducing tail rotor noise is also used. Engine noise (exhaust noise), power train noise and airframe noise becomes important at low rotor tip speeds and means must be found to reduce these noise sources if further noise reductions are desired. The use of a special test rig aids in isolating the various noise sources and arriving at the penalties (performance or payload) involved in quieting them. Significant noise reduction are achieved for the light helicopter with minimum performance or weight penalties because of the dominance of a single noise source (the tail rotor).
Noise Reduction Experience at Hughes Helicopter, Inc.
NASA/U.S. Helicopter Industry Workshop on Aerodynamic Noise Prediction/Noise Reduction ; 1982 ; Hampton, VA, US
1982-07-01
Conference paper
No indication
English
Evaluation of the Hughes 300 AG helicopter
SLUB | 1965
|Climatic Laboratory Survey Hughes YAH-64 Helicopter
NTIS | 1982
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