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Coupled finite element - boundary element calculation of sound transmission through windows

Langer, S. / Antes, H.

Increasing noise pollution requires more and better acoustic insulation of buildings. This 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, a model is presented for the calculation of sound propagation in complex air/glass pane systems. Numerically, the panes, the gas-filled space between them, and the interior of the building is 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 modelled by an adequate coupling condition. The principle of virtual work is applied to couple the FEM-modelling of the interior with the panes including the gas-filled space. The same principle is used to couple the window with the BEM-modelled exterior. The proposed method is applied to study the influence of pane configuration and thickness of panes or of the space between them on the transmission loss factor.