Structure Dynamics Analysis for Use in Noise Reduction of an Automotive Body-In-White

Structure dynamics of the car body-in-white fundamentally determines the interior noise level. Thus, modal analysis and response analysis should be carefully conducted in the noise and vibration reduction. In this study, eleven modes of a car body-in-white below the frequency of 200 Hz are tested and identified, and the frequency responses at several key points are analyzed. The first-order modal frequency of 34 Hz demonstrates that the NVH design of the car body-in-white is basically content. However, the regions around the engine mounting points and the trunk deck have a 15.5 Hz local torsional mode; Frequency response function at the engine mounting point 22 has a 23.5 Hz resonant frequency; Additionally, because there exist two resonant frequencies at 18 Hz and 24 Hz, respectively, within the normal excitation frequency range, remarkable vibration might be readily transmitted from the steering fixing point to the driver and induce noise. Therefore, to reduce the interior noise effectively, local stiffness around the engine mounting point 22, the trunk deck and the steering shaft fixing point 33 should be improved, and pertinent structure should be carefully refined.