US PATENT SUBCLASS 381 / 71.5
.~ Within duct


Current as of: June, 1999
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381 /   HD   ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES

71.1  DF  ACOUSTICAL NOISE OR SOUND CANCELLATION {7}
71.5.~ Within duct


DEFINITION

Classification: 381/71.5

Within duct:

(under subclass 71.1) Subject matter wherein the noise cancellation system cancels noise propagating in a tube, canal, pipe, or similar conduit, including automobile inlet and exhaust pipes.