Patent ID: 7600607

Claim:
A flow-through sound-cancelling muffler, comprising: a housing; a linear inner passage; an outer passage situated between said inner passage and an exterior wall of said housing, wherein a difference in length between said outer passage and said inner passage is selected from one-half a wavelength of sound to be canceled by the muffler and a multiple of said one-half wavelength of sound to be canceled by the muffler, said inner passage and said outer passage terminating in a common convergence chamber where sound propagating through exhaust gases in said outer passage destructively interferes with sound propagating through exhaust gases in said inner passage, and wherein said outer passage has walls made of heat conductive material to extract heat from exhaust gases passing through the outer passage and to conduct said heat to an exterior surface of said muffler; wherein said outer surrounds said inner passage; and wherein said outer passage has a zig-zag configuration.