A Combined FEM and BEM Approach for Sound Radiation with Finite Flange

This work develops a novel approach combining the finite element method (FEM) and the boundary element method (BEM) to implement an acoustic system that contains a vibrated structure radiating sound through an opening to the exterior domain. The opening is with a finite flange. The acoustic characteristics at the interface between the interior and exterior domains are also analyzed by determining the admittance matrix derived from the BEM model developed for the exterior domain. By doing so, the problem of acoustic behaviors in the interior domain is resolved using only FEM analysis. This proposed approach averts the disadvantages of asymmetry and lack of bandwidth encountered in the direct acoustic FEM-BEM coupling method, substantially reducing the computation time. This work also analyzes the throat impedance of a cylindrical horn to demonstrate the applicability of the proposed approach. The effects of flange size and wave frequency on impedance, sound pressure, and sound directivity are studied as well.