Cavity modes of a finite bounded region with rigid boundaries can be used to compute the steady state harmonic response for excitation of an acoustic cavity by a point source. In Cuboid domains, with analytical modes, this is straightforward. For more general regions, determining a set of orthonormal modes is more difficult. The finite element method could be used for arbitrary 3D regions.The current work investigates a hybrid numerical/analytical method, applicable to rooms of constant height, but arbitrary cross section. A 2D FE analysis is used to compute the cross-section modes/frequencies. 3D modes are constructed as an outer product of the cross section modes and 1D modes for the height. Comparison is made with BEM computations.
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