Coupled vibro-acoustic analysis in 3D using a wave expansion finite difference technique

The "mid-frequency gap" or "twilight zone" is what many authors refer to as the frequency band for which there is yet no established efficient modelling tool in vibro-acoustic analysis. This band usually extends from a few hundred hertz to about 1 KHz depending on the particular application, between the upper limit efficiency of traditional modelling techniques like finite elements, and the lower accuracy limit of non-deterministic approaches like SEA. The main challenge to alternative computational schemes, is to reduce the nodal density required to model the wave propagation in the fluid region whilst being robust and well conditioned at the same time. In this paper, a highly efficient wave expansion technique (introduced in ISMA25 [1] and presented also in ISMA2004 [2]) is used to model the fluid region in combination with a standard finite element approach for the structure. The technique is applied to a 3D conceptual car cabin model, showing to be much more efficient than finite element procedures.