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This paper discusses the methods of reducing weight of sound package through a new approach in sound absorption and insulation. In contrast to conventional sound package theory, a light porous material with high absorption (Ultra Light material) is used to replace a conventional porous/barrier sandwich material (classic), which results in an equivalent or better noise reduction in-vehicle with significant weight reduction. A Noise Reduction (NR) test was conducted with a box equipped with both the Ultra Light material and classic material. A SEA model of the same setup was also analyzed. Results from both the test and the analysis show that it is possible to achieve weight reduction by replacing conventional porous/barrier sandwich materials with light porous materials with high absorption.

Geometrical stiffening of the panels via rib design are considered due to vehicle design requirement and vibro-acoustic considerations. This paper studies the damping effectiveness of different damping treatments (extensional, shear damping structural damping layer - based on friction and inelastic collision) for flat panels and geometrically stiff panels. This paper considers the significant panel characteristics, damping efficiency of extensional and constraint layer dampers and structural damping layer. The overall vibro-acoustic reduction is measured over the low and medium frequency regions. The damping effectiveness on the panels is characterized by average vibration reduction, and frequency response function (FRF). The in-vehicle damping performance is measured experimentally with vibration excitation on in-vehicle size body panels.

Results of acoustical simulation of a vehicle with seats is presented in this paper, providing some basic understanding how the geometry of the seats as well as the acoustical properties of the seat material can affect the acoustical behavior of the interior. Both a finite element model and a boundary element acoustical model for a minivan with seats are generated. The influence of a change of seat geometry on modes and response is calculated first. In addition, the effects of acoustical properties of the seat material, i.e. airflow resistivity, on absorption respectively boom reduction is investigated. The simulation results have shown that the geometry of the seats has to be modeled quite accurately in order to achieve good simulation results. It has been found that rather small changes of the seat model may cause noticeable changes in modal behavior and acoustical response.

Optimization of component/system sound absorption can account for improvements in interior automotive sound quality. Components such as headliners, seats, etc., account for a large portion of a vehicle's available interior surface area and can provide significant sound absorption and thus improve sound quality if their sound absorption potentials are considered. In this paper, the authors attempt to convey a proper understanding of component absorption and its place in a vehicle interior system. The relation between sound absorption and component airflow resistance is discussed., and it is also shown that the processings for absorption materials have to be carefully designed. In order to evaluate the overall effectiveness of the absorption treatments, a reliable method for determining interior automotive reverberation times is reviewed.

A fully analytical method for the evaluation of noise reduction in a vehicle interior furnished with layered acoustic trim is presented. The method combines calculation of trim Transmission Loss (TL) and Absorption Coefficient with a Statistical Energy Analysis (SEA) calculation of trimmed panel Noise Reduction (NR). This allows for the evaluation of the trim package performance in real operating conditions and ranking of the different air-borne and structure-borne transmission paths.