Noise of Automotive Diesel Engines: Its Causes and Reduction 650165

A twelve year investigation of diesel engine noise due to combustion, particularly in the high-frequency range, has indicated that changes in engine structure can achieve substantial reductions in noise. Test results obtained at the Research Laboratory of CAV Ltd. showed that the predominant noise in diesel engines of automotive size is produced by the rapid pressure rise resulting from combustion. Work directed toward “smoothing” the cylinder pressure is still in progress. At the same time, it has been determined that two forms of engine structure could improve structural attenuation. They consist of a separate load-carrying structure with attached highly damped outer walls and a construction of great bending stiffness cast in low density material such as magnesium.