||This paper deals with a pressure-displacement formulation based on finite element method of an elasto-acoustic coupling problem. The direct solution of the resulting system is often CPU
intensive. To overcome this problem, only some structural modes in vacuum and some rigid cavity modes are always used. However, this classical pressure-displacement formulation leads
to unsymmetrical eigenvalue problems. In addition, if this method seems to be accurate for weak coupling, it can lead to significant errors when the truncated modes are coupled to some kept modes in the analysis.
In this paper, we propose a method combining the pseudostatic correction of the truncated modes in modal analysis with a symmetrization technique of the eigenvalue problems. It allows the calculation of the real coupled modes and frequencies as well as the computation of an accurate elasto-acoustic response, even for strong coupling of a structure with a heavy fluid (liquid), using less CPU time then the classical method since it leads to a diagonalized system.