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Dampers (PDs) are passive devices employed in vibration and noise control applications. They consist of a cavity filled with particles that, when fixed to a vibrating structure, dissipate vibrational energy through friction and collisions among the particles. These devices have been extensively documented in the literature and find widespread use in reducing vibrations in structural machinery components subjected to significant dynamic loads during operation. However, their application in reducing vehicle interior sound has received, up to now, relatively little attention. Previous work by the authors has proven the effectiveness of particle dampers in mitigating vibrations in vehicle body panels, achieving a notable reduction in structure-borne noise within the vehicle cabin with an additional weight comparable to or even lower than that of bituminous damping treatments traditionally used for this purpose.

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.

The use of small reverberation rooms for the measurement of the Diffuse Field Absorption Coefficient (DFAC) is common practice in the automotive industry. Such practice brings with itself a few issues, related to the limited size of the measurement environment. Some of these issues (e.g. measurements’ repeatability and reproducibility) have already been thoroughly investigated in articles published at past SAE NV Conferences. This paper intends to focus on some other “minor” aspects related to the measurement of DFAC in small reverberation rooms that so far have received little attention but that can, anyhow, have a non-negligible influence on the measurement results, in particular when they have to be compared to target curves.

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.

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.

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.

A poroelastic material can be represented as a material that is constituted by two phases: a structural phase given by a solid frame, and a fluid phase given by the air that fills the pores of the solid frame itself. In the mid frequency range, the physical behavior of both phases and their interactions need to be properly modeled in order to predict accurately the dynamic behavior of the porous material. This can be done using finite elements based on Biot's theory, which describes the macroscopic behavior of poroelastic materials by characterizing them through a set of parameters directly measured on material samples. In this paper, numerical/experimental correlations obtained using two commercial software programs that implement libraries of poroelastic materials are presented. A free-free steel plate covered by a 20mm thick layer of foam and a massive heavy layer has been selected as a first test case.

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.