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Porous materials are extensively used in the construction of automotive sound package parts, due to their intrinsic capability of dissipating energy through different mechanisms. The issue related to the optimization of sound package parts (in terms of weight, cost, performances) has led to the need of models suitable for the analysis of porous materials' dynamical behavior and for this, along the years, several analytical and numerical models were proposed, all based on the system of equations initially developed by Biot. In particular, since about 10 years, FE implementations of Biot's system of equations have been available in commercial software programs but their application to sound package parts has been limited to a few isolated cases. This is due, partially at least, to the difficulty of smoothly integrating this type of analyses into the virtual NVH vehicle development.

This paper shows that the combination of a glass and passive acoustic treatment manufacturers can bring different benefits and considerably improve the interior acoustics of a vehicle. Glazing contributes to the design of the vehicle in addition to its primary role, good visibility and safety. From an acoustic point of view, this brings a challenge for the interior comfort. Indeed, glazing has no absorption and classically has an acoustic insulation weakness around its coincident frequency. In most of the cases, these different aspects make glazing one of the main contributors to the sound pressure level in the passenger compartment, and the trend is not one of change. However, there are possible countermeasures. One of which is the use of laminated glazing with acoustic PVB. This solution allows reducing the loss of insulation performance at the coincidence frequency. The other is the usage of passive interior acoustic trims.

Generally all OEMs have a distinctive approach in designing their sound packages. Considering the complexity and combination involved in this process, there is no general valid scheme, although there tend to be some common blocks. Also as automotive manufacturers face strong demands to cut CO2 levels there is a trend to reduce prototypes and introduce limitations on weight of sound controlling materials. The supplier of the sound package must therefore be able to support the OEMs in taking design decisions early, quickly and based just on drawings, or even just on sketches in the concept phase. A proposed way forward in designing fast and cost-effective sound packages is by skillfully combining target setting, material characterization measurements, virtual prototyping and optimization tools. The solution should not only be acoustically effective, but also lightweight and cheap.

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.

The present work explains an innovative design methodology that allows efficient optimizations of vehicle body panels and treatments towards shorter development time and improved vehicle Noise and Vibration Harshness (NVH) characteristics. This tool named GOLD (Genetic Optimization for Lighter Damping), internally developed by Rieter Automotive, can be embedded into vehicle Computer Aided Engineering (CAE) design flow and can be then used in providing design and platform component sharing guidance information before prototype vehicles are available. GOLD is able to detect the optimal design of vehicle panel shape and damping packages with respect to NVH targets, by means of vibro-acoustic simulations. The core of this tool are the Genetic algorithms (GAs) which are heuristic methods which have been already successfully used, in several research fields, to solve search and optimization problems with a very large number of variables.