Investigations on mufflers for internal combustion engines

This paper deals with experimental studies on reactive types of muffler-and their combinations with absorption types-in order to determine their noise attenuation characteristics. Tests were carried out on a test rig, with a loudspeaker as the input source, as well as on a four cylinder diesel engine. The frequency spectra of attenuation levels, obtained experimentally, were compared with corresponding theoretical predictions. In addition, the effect on the performance of the engine itself was studied. The results showed, in general, a fairly good agreement between experimental results from test rig and theoretical predictions in the frequency range for which the latter is valid. The attenuation levels obtained from the mufflers fitted on the engine were, in general, lower. The effect on the performance of the engine was marginal. It was seen that the combination mufflers offer a good solution when high noise attenuation is desired