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.


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    Title :

    Passive Acoustic Range Estimation of Helicopters


    Contributors:
    R. Olson (author) / D. H. Cress (author)

    Publication date :

    1992


    Size :

    80 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English




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