A passive acoustic method is presented that determines the velocity of a moving helicopter and its range at the closest point of approach. This method requires only the use of a single microphone if the fundamental blade rotation frequency of the helicopter is known, or two spatially separated microphones if it is not. The blade rotation frequency is generally adequately known after the helicopter is correctly classified using acoustic signature characteristics other than those discussed herein. The range estimate is considered valid for ranges of a few hundred meters with the attendant assumptions that: (1) the helicopter is traveling in a straight line, (2) the helicopter is moving at a constant velocity, and (3) the main rotor of the helicopter has a stable revolution rate typical of present operational helicopters. The technique was successfully tested on an example helicopter.
Passive Acoustic Range Estimation of Helicopters
1992
80 pages
Report
No indication
English
Acoustic Detection , Aircraft , Aeronautics , Doppler systems , Position finding , Helicopters , Acoustic detectors , Airspeed , Passive systems , Range(Distance) , Acoustic tracking , Range finding , High resolution frequency estimation , Range estimation , Single acoustic detectors , Temporal coherence , Velocity estimation
Acoustic design for transport helicopters
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