HELICOPTER NOISE: STATE-OF-THE-ART

This paper reviews helicopter external noise with particular emphasis on the noise due to helicopter main and tail rotors. The bases for annoyance and audibility are discussed. Sources of rotor noise include steady, periodic, and random loads on the rotor blades, as well as volume displacement and nonlinear aerodynamic effects at high blade Mach numbers. Either main or tail rotors can be dominant noise sources at various frequencies and observer positions.

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