The exhaust noise from an engine is caused by the release of hot gas into the atmosphere in a series of high-pressure pulses, created when the exhaust valves open.
Although exhaust noise is made up of a wide range of different frequencies, it is possible to group the majority of the into three bands: low, medium, and high.
To attenuate exhaust noise, each band must be treated differently, and the silencer must be designed to reduce them harmoniously and simultaneously.
Exhaust gas after treatment components, soot filter elements and catalysts, show excellent acoustic performance in certain frequencies and can harmoniously complement the acoustic performance of the exhaust gas silencer/after treatment housing.
An unavoidable side effect of the silencer is an increase in back pressure which, if it exceeds the engine manufacturers limits, may decrease engine efficiency.