Northrop Grumman Systems Corporation

Basil Fedun

Paul N Turner

Peter E Madden

Michael P Johnson

A method and apparatus for reducing noise originating in a flowing stream of gases in which the noise is progressively absorbed from the flowing stream to provide noise of reduced intensity relative to noise intensity at the upstream end of the stream, and the noise of reduced intensity actively attenuated with controlled sound energy. To facilitate the active attenuation of noise, the flowing stream is preferably divided into a plurality of smaller streams after a level of reduced intensities is attained and the active attenuation performed independently in each of the smaller streams. The apparatus is in the nature of a conduit (10) which defines a single duct extending from the inlet end (14) for a portion of the length of the conduit. Downstream, the single duct joins with a plurality of ducts (32,34) extending to the outlet end (16). An active noise attenuating device is preferably provided in each of the plurality of ducts.

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Chardon, OH, United States of America

Basil Fedun