Analyses of Sound Transmission through Windows by coupled Finite and Boundary Element Methods

Increasing noise pollution requires more and better acoustic insulation of buildings. Such insulation design depends on several components where the component with the highest transmission rate dominates. Mostly, the windows take this part and, often, the sound transmission through windows is estimated by considering mainly the mass influence. Since this approximation is not sufficient for complex structures, the German Standards' Institute (DIN) demands that complex structures' transmission loss factors be determined experimentally and by certified agency. Those experiments are tedious and expensive and, therefore, numerical simulations are wanted. Here, for the analysis of sound propagation in complex air / glass pane systems a model is presented, in which the panes, the gas-filled space between them, and the interior of the building are treated by the Finite Element Method, whereas the sound distribution in the exterior space is calculated by the Boundary Element Method. The interaction between the parts of the structure and their environment is correctly modeled by an adequate coupling condition. The principle of virtual work is applied to couple the FEM-modeling of the interior with the panes including the gas-filled space. The same principle is used to couple the window with the BEM-modeled exterior. The proposed method is applied to study the influence of the pane configuration, of the panes' thickness and interspace on the transmission loss factor and to analyse the effect of different gas-fillings and of laminated glass on the sound insulation.