In this work the finite element method is applied to predict the acoustic behaviour of catalytic converters. Two different modelling techniques are considered and compared for the monolith: (1) First, the procedure described in previous works, in which the wave propagation in the monolithic catalytic converter is assumed to be analogous to the propagation in an equivalent fluid, characterized by its complex and frequency dependent impedance and wave number. In this case, the finite element model leads to the calculation of the three-dimensional acoustic field inside the complete catalytic converter, including the inlet/outlet ducts and the monolith. Therefore, this first approach allows the consideration of higher order modes inside all the catalyst components; (2) On the other hand, a coupling technique is applied in which the monolith is replaced by a plane wave transfer matrix, that is, only one-dimensional acoustic behaviour is allowed for the capillary ducts, while three-dimensional acoustic waves can still be present in the inlet/outlet ducts. The results provided by both approaches are compared with experimental measurements for a selected configuration, showing that the latter technique exhibits a better agreement. In addition, the effect of several parameters on the acoustic behaviour of the catalyst is investigated
