chamber 60 sound which does pass into third chamber 70 will be obstructed by column 90 which has space within it for further trapping transmitted noise finally third partition 75 while generally perpendicular to the exhaust flow though muffler 10 will present surfaces not perpendicular to second partition 65 and column 90 although separated from second partition 65 column 90 also serves to define the flow paths between column 90 and third partition 75 into channels reducing the amount of turbulence in the flow in that section as the exhaust gases flow through these channels towards convergence at second central aperture 80 auxiliary apertures 85 allow a portion of the exhaust gases to pass through third partition 75 reducing the pressure at second aperture 80 this reduces back pressure in the exhaust system by providing generous flow paths for exhaust gases while presenting internal sound barriers the present invention achieves the desired balance of sound attenuation with high flow rate and low back pressure while not shown in the drawings other embodiments utilizing multiple inlets and outlets are possible using two inlets would allow the exhaust from two separate banks of engine cylinders to pipe directly into the muffler this would avoid merging the individual exhaust pipes into a single pipe before joining the muffler an arrangement that can result in restrictive flow in the single pipe using two outlets would increase the flow rate out of the muffler and further reduce back pressure other embodiments not illustrated.