The vibration and acoustic behaviour of the internal combustion engine is a highly complex one, consisting of many components that are subject to loads that vary greatly in magnitude and which operate at a wide range of speeds. The interaction of these components and the excitation of resonant modes of vibration is a major problem for the powertrain engineer when optimising the noise and vibration characteristics of the engine. This paper summarises a study that has been undertaken to assess and optimise the dynamic behaviour of a current production diesel engine with the objective of reducing radiated noise from the engine. The dynamic behaviour of the diesel engine has been assessed using simulation tools. The dynamic analysis will predict the forces and displacements at each of the nodes of the model by forced response analysis. Predicted results and experimentally measured values were found to be in close agreement. A number of production feasible design modifications have been considered and analysed. Structural modifications viz. ribbing pattern, stiffeners and gusset additions were suggested by taking reference of NSI findings to improve the overall stiffness of the engine assembly. It has been demonstrated that by changing material such as visco elastic material gives reductions in radiated noise. The hybrid approach so used helped in reducing noise level of engine to meet set noise level targets with a minimal increase in overall mass.