The solution of complex acoustic problems of the low-frequency sound field presupposes the numeric implementation of the wave equation. Especially for the calculation of sound fields in a finite volume (interior problem), the method of the finite elements (FEM) can be applied. The software market gives the acoustic engineer many different commercial simulation packages, which have no or only a limited user interface for user extensions. This was the reason to create the simulation module called WaveSolve3D. Due to its high portable structure WaveSolve3D can be used on all current and future computer generations, and thereby permits the running of the application on the hardware with the best computing power. In the context of this paper some simulation results computed by WaveSolve3D will be presented. Verification can be achieved by comparison with analytical results in simple enclosures or with measurement results for more complex rooms. The work is part of a project which intends to extend the frequency range in room acoustical computer simulation.