The design of automotive components for low structure-borne interior noise and vibration requires the ability to reliably simulate total vehicle system response over a wide operating frequency range. This implies that the car body, its interior acoustic cavity, and critical structural components must be included in this overall dynamic model.
Unfortunately, most noise and vibration problems occur in the 200-1000 Hz frequency range where existing finite element and experimental modal methods have limited applicability. This is due to the high modal density, high damping levels, and sensitivity to fine geometric detail. Moreover, it is highly doubtful that these methods will ever be practical tools for the study of the total body dynamics over the frequency range of 200-1000Hz.
In this paper, a practical hybrid experimental-analytical approach is proposed in response to the need to simulate high frequencies structure-borne noise and vibration in automotive systems. This approach was developed out of a recognition that low and moderate modal density automotive components can be modeled reasonably well using existing finite element methods. High modal density body dynamics are best represented by experimental frequency response functions to eliminate theoretical modeling errors. This method allows for the identification of critical components by noise path analysis and the evaluation of specific design modifications for those components represented by finite elements. The procedure is based on the structural modification analysis using response technique (SMART), which is a variation of the classical dynamic impedance method. It includes a mixture of stiffness and flexibility formulations for the system assembly. Several concepts have also been incorporated in the proposed procedure to improve its practicality and numerical robustness.