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Title: Passive acoustic range estimation of helicopters
Authors: Cress, Daniel H.
Olson, Reo
Keywords: Doppler effect--Military aspects
Military reconnaissance
Publisher: Environmental Laboratory (U.S.)
U.S. Army Engineer Waterways Experiment Station.
Series/Report no.: Technical Report;EL-92-13
Abstract: 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: (a.) the helicopter is traveling in a straight line, (b.) the helicopter is moving at a constant velocity, and (c.) 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.
Appears in Collections:Technical Report

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