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This paper explores the performance of light weight attenuators, which take a dissipative approach to sound abatement in the motor vehicle. An analytical model is used to predict the sound transmission loss and random incidence sound absorption of attenuators, absorbers and sandwich insulation systems. Then, a mathematical expression is developed which combines the dissipative and sound transmission loss performance to determine the total noise reduction provided in the vehicle. Using this equation, the performance of multi-layered attenuators is shown to be comparable to, or better than that of sandwich insulators. Finally, test results from various studies in vehicles show that significant weight savings can be realized by using these multi-layered attenuators, which take a dissipative approach to vehicle sound insulation, rather than the traditional sandwich insulation system.

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.

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.

Although geometric stiffeners (ribs, beads, dimples, etc.) may initially appear to reduce the low frequency (<300 Hz) sound radiation capacity of otherwise flat panels, when sensitivity to treatment and automobile excitation mechanisms are considered, no significant acoustic or vibration benefits are apparent. Testing does reveal that stiffeners reduce the number of low frequency resonance modes, but add on vibration treatments are unavoidable since not all of the resonance modes can practically be raised to frequencies above primary engine excitation. Further, after even relatively Light treatments are added, flat panels exhibit lower Intuition might suggest that since increased panel stiffness can effectively reduce the overall surface velocities of untreated panels, add on treatments can be reduced and current sound levels will be maintained. However, this is not the case.