SUMMARYFlexible discretization techniques for the approximative solution of coupled wave propagation problems are investigated, focussing on aero-acoustic and elasto-acoustic coupling. In particular, the advantages of using non-matching grids are presented, when one subregion has to be resolved by a substantially finer grid than the other subregion. For the elasto-acoustic coupling, the problem formulation remains essentially the same as for the matching situation, while for the aero-acoustic coupling, the formulation is enhanced with Lagrange multipliers within the framework of mortar finite element methods. Several numerical examples are presented to demonstrate the flexibility and applicability of the approach.