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Prediction of the drive-by noise level in the early design stage of an automotive vehicle is feasible if the source signatures and source-receiver transfer functions may be determined from simulations based on the available CAD/CAE models. This paper reports on the performance of a drive-by noise synthesis procedure in which the transfer functions are numerically evaluated by employing the Fast Multipole Boundary Element Method (FMBEM). The proposed synthesis procedure first computes the steady-state receiver contributions of the sources as appearing from a number of vehicle positions along the drive path. In a second step, these contributions are then combined into a single transient signal from a moving vehicle for each source-receiver pair by means of a travel time correction.

In many industrial applications, such as in the automotive and machine building industry, there is a continuous push towards lightweight materials motivated by material and energy savings. This increased use of lightweight materials, however, can strongly compromise the Noise, Vibration and Harshness (NVH) performance of the final products. Especially in times where the NVH performance not only receives a higher legislative attention, but also becomes a commercial differentiator, this also represents a key point of attention for designers and directs research activities towards new experimental and numerical techniques to accurately predict the NVH performance of lightweight systems as early as possible in the design process. The presented work discusses novel measurement setup, specifically developed for examining the vibro-acoustic behavior of lightweight structures. The test stand consists of a concrete cavity of 0.83 m₃.

The combination of lightweight design and performant Noise, Vibrations Harshness (NVH) solutions has gained a lot of importance over the past decades. Lightweight design complies with the ever more stringent environmental requirements, however conflicts with NVH performance, as low noise and vibration levels often require heavy and bulky systems, especially at low frequencies. To face this challenge, locally resonant metamaterials come to the fore as low mass, compact volume NVH solutions, beating the mass law in some tunable frequency zones, referred to as stopbands. Metamaterials are artificial materials made from assemblies of unit cells of non-homogeneous material composition and/or topology. The local interaction between unit cells leads to superior performance in terms of noise and vibration reduction with respect to the conventional NVH treatments. Previously the authors showed how wave propagation along one-dimensional structures can be reduced by metamaterial additions.

This paper presents a newly developed hybrid simulation technique for uncoupled acoustic analysis of interior cavities. This method applies a Wave Based model for a large, geometrically simple portion of the acoustic cavity. The superficial details of the problem domain are modeled using a modally reduced finite element model. The resulting hybrid model benefits from the computational efficiency of the Wave Based Method, while retaining the Finite Element Method's ability to model the actual geometry of the problem in great detail. Application of this approach to the analysis of a moderately simplified acoustic car cavity shows the improved computational efficiency as compared to classical finite element procedures and illustrates the potential of the hybrid method as a powerful tool for the analysis of three-dimensional interior acoustic systems.