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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.

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.

Automotive suppliers provide multi-layer trims mainly made of porous materials. They have a real expertise on the characterization and the modeling of poro-elastic materials. A dozen parameters are used to characterize the acoustical and elastical behavior of such materials. The recent vibro-acoustic simulation tools enable to take into account this type of material but require the Biot parameters as input. Several characterization methods exist and the question of reproducibility and confidence in the parameters arises. A Round Robin test was conducted on three poro-elastic material with four laboratories. Compared to other Round Robin test on the characterization of acoustical and elastical parameters of porous material, this one is more specific since the four laboratories are familiar with automotive applications. Methods and results are compared and discussed in this work.

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.

The recently updated pass-by noise measurement procedure prescribes a mix of acceleration tests and constant speed tests. This has led to an increased relevance of tire noise relative to the past, when the procedure prescribed only acceleration tests. In addition, the next phase of the roadmap for pass-by noise limits for passenger vehicles is 70 dB(A) by 2020, later followed by 68 dB(A). In this context, exterior tire noise has drawn increasing attention. OEMs, suppliers of passive acoustic treatments, road manufacturers and tire manufacturers are, at the moment, devoting strong efforts to the definition of solutions for the control of exterior noise. This paper is concerned with the potential of existing passive exterior treatments to reduce the exterior noise generated by the tires. Different countermeasures are analyzed, namely wheelhouse liners, under-engine shields, under-body panels and under-trunk panels.

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.

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.