Passive Acoustic Range Estimation of Helicopters

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 micro...

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Bibliographic Details
Main Authors: Olson, Reo, Cress, Daniel H
Format: Report
Language:English
Subjects:
Acoustic Detection and Detectors
ACOUSTIC DETECTORS
ACOUSTIC TRACKING
Aerodynamics
AIRSPEED
DOPPLER SYSTEMS
Helicopters
HIGH RESOLUTION FREQUENCY ESTIMATION
MU-001
PASSIVE SYSTEMS
PE62719A
POSITION FINDING
RANGE ESTIMATION
RANGE FINDING
RANGE(DISTANCE)
SINGLE ACOUSTIC DETECTORS
Target Direction, Range and Position Finding
TEMPORAL COHERENCE
VELOCITY ESTIMATION
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Summary: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.