Fast Acoustic Trim Modeling using Transfer Admittance and Finite Element Method

Finite elements have been successfully used over the past decade to predict the vibro-acoustic behavior of complex large systems as encountered in the transportation industry. Nevertheless, some challenges are still not completely solved as for instance the modeling of multilayer porous materials used to reduce the noise in cavities. A simple model based on local impedance and added mass has been widely used in the past to model those acoustic trim materials at low frequency but shown limitations when the frequency range increases. To circumvent this limitation, approaches based on finite element formulations have been developed to model the poroelastic materials. They range from simple equivalent fluid models to complex models involving a solid phase and a fluid phase. However, those approaches require important modeling effort, computer memory and solution time.

A unique approach to model acoustic trim material is presented in this paper. The approach is based on transfer admittance coupled to standard FEM. The transfer admittance can be either measured, computed using the above mentioned complex FEM approaches or computed using analytical wave-based approach. The technique enables the engineers to rapidly and accurately model the trim materials and assess their effects in the global vibro-acoustic system.

The method is presented in this paper together with validations using a full FE solver and experimental validations. The experimental set-up consists of a plate backed cavity with three configurations: bare plate, plate covered with a porous material and a plate covered with a porous material and a heavy viscoelastic layer. Very good agreement has been found between the proposed approach and the experimental results.