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105 APPENDIX 3Ndb 90 LEVELS acoustical signature aircraft noise aircraft sounds amplitude amplitude-time history analysis Comparative Peak Perceived comparative peak PNdb configuration CRUISE MEASURED PNdb cruise noise cruise operation CYCLES PER SECOND Doppler shift electronically fan lift VTOL feet flight FREQUENCY IN CYCLES Helicopter Rotor inlet noise jet airplane jet lift VTOL l5 decibels lift engine LIFT JET magnetic tape main rotor MEASURED PNdb LEVELS Noise Reduction Required noise signature OUTDOOR PNdb LEVELS peak perceived noise perceived noise level PNdb 95 predicted propeller noise pure tone RESULTS OUTDOOR PNdb rigid rotor VTOL rotational noise Rotor Cruise Spectrum rotor noise SECOND Figure shaped random noise simulated SOUND LEVEL METER speaker spectrum shape stimulii SUBJECTIVE RESPONSE SUBJECTIVE TEST RESULTS Synthesis of Aircraft synthesized tail rotor takeoff TANDEM ROTOR CRUISE tandem rotor helicopter Tandem Rotor VTOL terminal noise terminal operation test subjects Tilt Wing VTOL tip speed Turbofan STOL Turboshaft vehicle