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With the recent development of technologies for interpreting vibration and noise of vehicles, it has become possible for carmakers to reduce idle vibration and driving noise in the phase of preceding development. Thus, the issue of noise generation is drawing keen attention from production of prototype car through mass-production development. J. D. Power has surveyed the levels of customer satisfaction with all vehicles sold in the U.S. market and released the Initial Quality Study (IQS) index. As a growing number of emotional quality-related items are added to the IQS evaluation index, it is necessary to secure a sufficiently high quality level of low-frequency speaker sound against rattle noise. It is required to make a preceding review on the package tray panel, which is located at the bottom of the rear glass where the woofer speakers of a passenger sedan are installed, the door module panel in which the door speakers are built.

Design optimization of a vehicle is required to increase a product value for noise and vibration performances and for a fuel-efficient car. This paper describes the development process of a high stiffness and lightweight vehicle. A parameter study is carried out at the initial stage of design using the mother car, and a design guide with a good performance is achieved early prior to the development of the proto car. Influences of body stiffness based on the relative weight ratio of the floor and side structures are analyzed. Results show that bending and torsional stiffness has a significant effect on weight distribution ratio. Influences of the distribution of side joint stiffness are analyzed through numerical experiments. Results reveal that the stiffness difference between the upper and lower parts should be small to increase the stiffness of a body.

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.