Noise Reduction of Engines by Structural Modifications

This paper describes the efforts made on an in-line 6-cylinder diesel engine to identify its major noise sources and to reduce their contribution by means of structural modifications, in order to achieve a 3 dBA reduction in the engine overall noise level. Both acoustic intensity and modal analysis techniques were used to identify the important noise sources on the engine and their dynamic characteristics. Modifications to the important sources were designed using experimental, analytical, and plastic modelling techniques. The modifications which included stiffening, damping, and isolation were applied to the engine and their effectiveness verified under typical operating conditions.