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In automotive acoustics, body NVH design is traditionally carried out without considering the acoustic trim parts. Nevertheless, the vibro-acoustic interaction of body structure and insulation trim cannot be neglected in the middle frequency range, where structure borne propagation might still be dominating and where classical statistical approaches are generally not able to represent the influence of local changes in stiffness and damping. This, together with the market requirement of lightweight and more efficient sound package solutions, is leading the CAE engineers to evaluate new design approaches dedicated to vehicle components such as dash or floor systems, for which the multi-physics interaction between damping, body stiffness and trim impedance is important.

Due to the pressure on CO₂ reduction, during the last years "lightweight" parts have become rather popular, as opposed to "conventional" parts, traditionally constituted by a heavy mass layer on top of a soft decoupler. While "conventional" parts are based on pure insulation, "lightweight" parts propose some kind of compromise between absorption and insulation. This makes their design difficult: designing a "lightweight" part means adjusting in the proper way the balance between the absorption and the insulation provided by the part itself and the search for an optimal balance has to take into account relevant vehicle-dependent boundary conditions. Typically, in the design of a lightweight dash insulator a key role is played by the presence of the instrumentation panel and by the importance of the pass-throughs. This article describes a procedure that can help the NVH engineer in the above-mentioned task.

Typically, in the automotive industry, the design of the body damping treatment package with respect to NVH targets is carried out in such a way to achieve panel mobility targets, within given weight and cost constraints. Vibration mobility reduction can be efficiently achieved thanks to dedicated CAE FE tools, which can take into account the properties of damping composites, and also, which can provide their optimal location on the body structure, for a minimal added mass and a maximized efficiency. This need has led to the development of different numerical design and optimization strategies, all based on the modeling of the damping composites by mean of equivalent shell representations, which is a versatile solution for the full vehicle simulation with various damping layouts.