Application of a directly coupled boundary element and finite element model to the dynamics of coupled acoustic silencers

A BEM code consisting of three-node isoparametric triangular continuous elements to discretize the acoustic cavity system was developed in this research. This BEM code deals with the dynamic analysis for any arbitrary shaped acoustic cavity model which exhibits boundary conditions such as a known pressure, velocity and impedance, and a point source within the acoustic domain. This BEM code was verified as to its increased accuracy and usefulness over one using constant elements.; The FEM code used for the shell structure analysis was obtained by combining a plate bending element, PAT (83) and a plane stress element. The model's accuracy was verified using several structural configurations.; These BEM and FEM models were coupled and used in investigating the dynamics of a coupled structural acoustic system model with flexible vibratory walls. The coupled BEM-FEM code implemented was verified by comparing its predicted results with solved known analytical and experimental solutions for several specified models.; The acoustic silencer's transmission loss (TL) was predicted using a four-pole parameter matrix theory model and the BEM results for a specified reactive muffler configuration without flexibility first. Then the effects of the muffler's structural flexibility using the four-pole parameter matrix theory and the coupled BEM-FEM results were taken into consideration. The resulting sound pressure levels radiated from the flexible wall and tailpipe exit of the reactive muffler, were approximated by using the structure and acoustic informations provided by the model. Then the effects of varying the structural flexibility on the radiation of the muffler were investigated.