The solution of coupled interior/exterior acoustic problems using the boundary element method

The boundary element method (BEM) is used to solve a class of problems in which an interior domain and an exterior domain are coupled by an interface surface, such as when sound propagates along a duct and radiates from the open end into the surrounding space. In the current approach, integral equations for the interior and exterior domains are coupled using continuity conditions at the interface surface between the two domains. The integral equations are reduced to numerical form using second-order boundary elements. The coupled interior/ exterior boundary element method presented here overcomes numerical error and excess computer time problems present when traditional boundary element formulations are applied to this class of problems. The current approach is illustrated using several examples including: the radiation of sound from an open duct, the radiation of sound from a source within a partial enclosure, and the acoustical response of a slotted cavity due to an incident plane wave.