Sound Transmission Loss Prediction of a Wiring Grommet by Using the FEM

This paper focuses on predicting the sound transmission loss (STL) of a wiring grommet using the finite element method (FEM). The wiring grommet is used to reduce the noise transmitted through a wiring hole and is combined with a wiring harness passing through the wiring grommet. To predict the STL of the wiring grommet combined with the wiring harness, an FEM analysis was performed in the following two steps. In the first step, appropriate assembly conditions were applied to account for the change in the dynamic characteristics of the wiring grommet due to its coupling with the wiring harness. The outer diameter of the wiring harness is slightly greater than the internal diameter of the wiring grommet, resulting in a contact pressure on both sides. Because of the change in the dynamic characteristics of the wiring grommet due to such a contact pressure, the coupling conditions were considered. In the second step, an acoustic analysis was performed considering the viscoelastic characteristics of the wiring grommets with frequency dependent storage and loss modulus. Finally, the effect of the wiring harness on the STL of the wiring grommet was examined, and the validity of the modeling was verified by comparing with the STL measurement results.