Power-based approach for assessment of structure-borne sound in mechanical networks of vehicle structures

The vibroacoustic assessment and optimization of vehicle components at the early stage of complete vehicle development is an essential competitive factor. For the low and mid-frequency range mainly transfer functions are used, which are formulated in primary variables like forces or displacements. This approach, however, considers only a part of the whole variables of a harmonic dynamic system. For this reason many methods are available, based on the evaluation of the structure-borne sound power in dynamic structures, as this real scalar quantity combines phase-correct the force and velocity measures. As power indicates the energy flow in the system, the energy transmission paths in a system can be visualized. Based on this concepts a deterministic approach in the frequency domain is presented, suited for the analysis of the structure-borne sound mean power in typical vehicle related framework-like structures. These structures, which are assumed to be linear and in steady state, are condensed to a network representation of substructures. The energy exchange of this subsystems is evaluated at discrete frequencies by means of active mean power. Since in the early stage of vehicle development only numerical simulations exist, Finite-Element models are the basis for analysis. The mean power quantities therefore are calculated as an postprocessing-step from the displacement solution.