Abstract: A muffler comprising a housing having inlet and outlet ends and having a venturi tube of smaller diameter than the housing disposed therewithin in communication with its outlet end is disclosed. The venturi comprises a first bell reducer, which reduces the cross-sectional area of the venturi to substantially half its original value, a straight tubular section of cross-sectional area equal to the reduced area and of as great length as possible within the venturi, and a gradually diverging section connecting the straight section of reduced area to a perforate tube, of substantially equal area as the inlet of the venturi and communicating with the outlet of the housing. Several distinct embodiments of the invention are disclosed, which vary by means causing additional diversion of the gases from their straight path.