A validation study of the structural modification technique for vibro-acoustic analysis

Abstract

The structure-borne noise inside the passenger cabin of automobiles, which is mainly caused by the vibrating panels enclosing the vehicle, dominates the low frequency noise. The structural design of the panels can be modified to improve the sound pressure level (SPL). The sound pressure level (SPL) can be predicted using a vibro-acoustic model which includes the Finite Element Model (FEM) for the structural analysis and the Boundary Element Model (BEM) for the acoustic analysis. However, when the designer is making changes on the structural model to improve the SPL, the vibration analysis must be repeated after every modification before the reanalysis of the vibro-acoustic model. Such changes require considerable computational time especially in case of very complex structures. In our previous studies, it has been shown that the structural modification technique can be implemented to reduce the computational time significantly by skipping the modal analysis of the modified structure. This technique utilizes the frequency response functions (FRFs) of the original model for the reanalysis of the structure that is subjected to structural modification. In this study, a demonstration testbed of a rectangular box with the flexible mid-panel is constructed in order to validate the structural modification technique experimentally and determine the effect of modification. The differences between the numerical and experimental models are discussed then the structural/acoustic performance of the rectangular box is compared before and after the modification using the testbed results.