Modelling Acoustic Trims in FEM, an Overview of the Different Simulation Methods

The need for the industry to simulate and optimize the acoustic trim parts has increased during the last decade. There are many approaches to integrate the effect of an acoustic trim in a finite element model. These approaches can be very simple and empirical like the classical non-structural mass (NSM) combined to a high acoustic damping value in the receiver cavity to much more detailed and complex approach like the Poro-Elastic Materials (PEM) method using the Biot parameters. The objective of this paper is to identify which approach is the most appropriate in given situations.

This article will first make a review of the theory behind the different methods (NSM, Impedances, Transfer Matrix Method, PEM). Each of them will be investigated for the different typical trim families used in the automotive industry: absorber, spring/mass, spring/mass/absorber. An academic (flat plate and cavity) and an automotive based test case with thickness distribution variation over the trim part will be studied. For each case, the results will be discussed and the best compromise for modeling time and results quality will be identified. The analysis will focus on full FE models up to 400Hz excited by structure borne and airborne excitations.