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The ability to predict the interior acoustic sound field in a vehicle is important in order to avoid or to minimize unwanted noise conditions, such as boom or high pressure levels at cavity resonance frequencies. In this work an acoustic modal analysis is carried out for a minivan. The testing procedure is discussed and some results are shown. With the seats removed and for low frequencies the interior of the vehicle is similar to a rectangular box for which an analytical solution exists. At higher frequencies and with the seat, the interior acoustic field displays complex mode shapes.

Concepts for dual density materials for usage as absorbers and decouplers are based on well-established layered media principles and have been applied for many years in non-automotive applications. Balancing the mass, air flow resistance, and thickness allows for improved noise attenuation in the low to mid frequency range which is of particular interest for automotive NVH management. Using these principles, products were tuned via mass and airflow resistance to reduce noise levels while also significantly reducing mass. Validation in various vehicles confirmed that up to a 55% reduction of a sound package's mass is possible. The considerable weight reductions of dash insulators and carpet systems are possible at the same times as the sound level in the vehicle interior is at least maintained and frequently improved.

Some common assumptions used in simplifying vehicle NVH prediction and design, in conjunction with isolators and mounts, are examined with the aim of offering qualitative improvements. It is often assumed that only the translational degrees of freedom are sufficient for a detailed structural analysis. Errors introduced by this simplification are quantified for some illustrative and simple examples concerning isolators, coupled analyses and transfer path analyses. It is suggested that a complete measurement procedure can alleviate the need for assuming beforehand that the rotational degrees of freedom are not essential. Once obtained they can be disregarded if demonstrated unnecessary.