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A new method for analyzing idle shake is discussed. A primary design technique of engine mount systems and vehicle bodies in the early development stage is proposed. In general, specifications for the engine mount system, which is composed of several insulator rubbers, are determined by certain criteria of transmissibilities of engine excitation forces to the rigid foundation. However, when the transmitted forces are applied to a flexible body, the resultant response of the body depends not only on the transmissibilities of the isolation system, but on vibratory characteristics of the flexible body. Therefore, the body needs to be taken into account for antivibration design as well as the engine mount system. Besides, the engine mount and the body cannot be evaluated by simple criteria due to the several insulator rubbers which feature many transmissibilities and transfer functions.

For the booming noise reduction by vibration mode control, structural and acoustic analyses or optimization procedure have been studied. For obtaining know-how to reduce booming noise, it is necessary to understand the mechanism of vibration phenomenon, and then to simplify the phenomenon. In this paper, it is presented that the booming noise should be reduced by using the simplification of panel vibration mode of vehicle body. Simplification is obtained by considering that panels are forced and vibrated by the body frame of the vehicle, and that panel vibration is decided by frame movement and stiffness and mass distribution in the panel. The simplification about panel vibration control by the appropriate mass and stiffness distribution is confirmed by using floor vibration. By appropriately controlling the stiffness distribution in the dash panel, booming noise caused by the dash panel vibration was reduced.