Noise Sensitivity Analysis of an Engine Mount System Using the Transfer Function Synthesis Method

The transfer function synthesis method is one of the most powerful methods in analyzing the responses of complex built-up structures under high modal density. Its superiority mostly comes from the ability to incorporate experimental FRFs into the formulation. In this paper, a general procedure for the design sensitivity analysis of vibro-acoustic problems has been presented in frame of the transfer function synthesis method. For an acoustic response function, the proposed method gives a parametric design sensitivity expression in terms of the partial derivatives of the connection element properties and the transfer functions of the substructures. As a realistic problem, an interior noise problem in a passenger car is analyzed. The proposed noise sensitivity formulation calculates the interior noise variations with respect to the changes of the dynamic characteristics of the engine mounts and the bushes. To obtain the FRFs, a finite element model is built for the engine mount structures, and experimental FRFs are used for the trimmed body including cabin cavity. The comparison of interior noise sensitivities obtained by the proposed method and the finite difference method shows that the proposed method is efficient and accurate.