An improved method for the design of expansion-chamber mufflers is described and applied to the task of reducing exhaust noise generated by a helicopter. The method is an improvement of standard transmission-line theory in that it accounts for the effect of the mean exhaust-gas flow on the acoustic-transmission properties of a muffler system, including the termination boundary condition. The method has been computerized, and the computer program includes an optimization procedure that adjusts muffler component lengths to achieve a minimum specified desired transmission loss over a specified frequency range. A printout of the program is included together with a user-oriented description. (Author)


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    Title :

    An Improved Method for Design of Expansion-Chamber Mufflers with Application to an Operational Helicopter


    Contributors:

    Publication date :

    1973


    Size :

    73 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English