The prediction of sound-fields in closed volumes with vibrating delimiting surfaces is typically carried out by the use of energy methods. Those methods are robust for subsystems with high modal densi-ty, if the averaging over frequency bands, points of excitation and points of observation is carried out. However their performance is limited if the spatial resolution of the response has to be described and if boundary conditions are investigated more in detail. They fail when impulse responses shall be calculated. By the use of the Finite Element Method (FEM) for the coupled fluid-structure system those deficits would theoretically be eliminated; however this requires extensive calculations and leads to non robust results in case no averaging is done in the post-processing. Considering the fact, that for many applications a limited frequency range is of interest and that the development of the FEM is continuously progressing, the research project 2-5 deals with a systematic procedure to calculate frequency-response functions (FRF) and impulse response functions in room-acoustics by means of the FEM. The method is based on a modal approach for the fluid, using the component mode syn-thesis to reduce the effort of calculation, in case design changes should be studied. For simple geo-metries – which often occur in civil engineering - the modes can be found by closed form solutions. Free interface eigenmodes or wave number approaches are used at the coupling interface to model the deformation pattern. In addition, focus is laid on the description of various absorbers. Whereas plate-resonators are described by wave number- or local impedances, porous absorbers are modeled by the help of the Theory of Porous Media (TPM). The results of the modeling are compared with results of industrial applications and applications in civil engineering where reradiated sound plays an important role.