Investigation of Silencing Characteristics of Mufflers : 2nd Report, Silencing Characteristics for Exhaust Noise

Abstract

Attenuation characteristics for exhaust noise are influenced by the exhaust gas temperature, flow velocity and non-steady wave. They are investigated theoretically and experimentally by using a specially designed apparatus. Gas temperature has an effect to modify frequency of the attenuation curve without change of attenuated amount, and the effect of flow velocity is negligibly small. Attenuation characteristics for non-steady wave is similar to the one for pure sound, but audible sound inetensity is much larger (about 40 db) than one indicated by instruments. Attenuation characteristics of chambers filled with glass wool are obtained experimentally, and this type shows much efficacy for non-steady wave. Results of the experiments in which mufflers are inserted in the engine exhaust line, agree with those of the theories which are composed of equations on muffler themselves, tail pipe and effects of gas temperature, flow velocity and non-steady wave.