Full-scale Rotorcraft Broadband Noise Prediction and its Relevance to Civil Noise Certification Criteria

Rotorcraft broadband noise prediction and its relevance to civil noise certification criteria are demonstrated for a full-scale helicopter. It is shown that prediction of the effective perceived noise level (EPNL) during steady level flight can be signi ficantly improved by incorporating rotor broadband noise mechanisms in combination with main and tail rotor discrete frequency noise sources. EPNL is significantly under-predicted if rotor broadband noise mechanisms and/or tail rotor noise sources are ignored. EPNL for future rotorcraft can be improved if design efforts concentrate on the rotor design parameters (in order of priority) that effect: 1) Tail rotor discrete frequency noise, 2) Main rotor broadband noise, and 3) Main rotor discrete frequency noise.