Modelling the sound transmission across junctions of building components by energy influence coefficients

A trend towards lightweight structures, e.g. timber structures, is noticeable in civil engineering, which implies the necessity to predict vibroacoustic characteristics like the transmission of structure-borne sound in order to fulfil requirements regarding serviceability. This contribution focuses on the investigation of junctions of building components e.g. between wall and ceiling. It is part of a joint research project with the aim to catalogue the coupling for a variety of junctions. The resulting database may serve to predict the transmission of structure-borne sound which is typically carried out either using a Finite Element (FEM) approach, suitable for the low frequency range, or by means of energy methods like the Statistical Energy Analysis (SEA) for the high frequency range. Therefore the so-called mid frequency gap emerges, which is examined and attempted to be closed. In this context SEA-averaging techniques are applied in the postprocessing of FEM calculations to obtain an adapted "SEAlike" approach. By varying the subsystems to be excited it is possible to determine Energy Influence Coefficients (EIC), which describe the specific energy content of the different subsystems with respect to the input power. Using this hybrid approach vibroacoustic predictions can be performed also in the mid frequency range. Inverting the EIC-matrix Coupling Loss Factors as well as Damping Loss Factors of the different subsystems can be calculated if the subsystem definition fulfils the SEA-requirements. The application of the method in combination to a classical SEA calculation and to laboratory measurements is presented.