Paul H Turner

US Patent:

56505990, Jul 22, 1997

Filed:

May 8, 1995

Appl. No.:

8/439055

Inventors:

Peter E. Madden - Shaker Heights OH
Basil Fedun - Chardon OH
Paul N. Turner - Concord Township OH
Michael P. Johnson - Shaker Heights OH

Assignee:

Northrop Grumman Corporation - Los Angeles CA

International Classification:

B64F 126

US Classification:

181218

Abstract:

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.