Abstract: A muffler for internal combustion engines, compressed air tools and the like, has a tubular core with one end having a connection with a source of exhaust gases and the other end closed or valved in such manner as to prevent build-up of back pressure with an increase of exhaust gas flow above a selected maximum. Intermediate its two ends a length of the core is perforated around its entire periphery. A succession of dished annuli are fitted about a perforated area of the core with alternate annuli reversed so that they are arranged in several pairs with the peripheral edges of each pair converging to form between them an attenuation chamber from which gases entering the chambers through the central core escape at the peripheries of the chambers, the larger circumference of the gas escape passages at the peripheries of the chambers in relation to the gases entering the chambers through the perforations in the tube relieving the pressure while the sound is attenuated to a greatly reduced level.