During the last 5 years, the so-called "hybrid" insulating-absorbing sound package components have increased their importance due to the strong pressure to cut weight in vehicles. Unlike conventional insulators, based on the well-known spring-mass principle, these hybrid components have two features of interest: 1) A light "heavy layer", made with pressed felt, with a positive impact on total weight of the component. 2) A tunable capability of absorption able to exploit the reflections in the acoustic cavity of the instrumentation panel. Of course, the reduction of weight of heavy layer is, in general, a negative feature for insulation. The strategy to combine insulation and absorption in a way to the keep same performances and reducing weight at the same time is the main engineering task of this application. In this paper, first an overview is provided about the different "hybrid" technologies and their penetration in the automotive market, with an analysis of their main opportunities and drawbacks. Then, a new technology, based on a fibre-foam combination exploiting the concept of dynamic stiffness control, is described. It allows a weight-effective local adjustment of the insulation and absorption properties of the sound package component. Local increase of insulation is achieved by controlling the material properties of the fibre layer, rather then using heavy patches of rubber-based materials. Based on this concept, simulation models of the component were developed, relying on the Biot's theory for porous materials and on the transfer matrix method. Such models were subdivided into areas where the properties of insulation and absorption can be changed, in order to generate a high number of possible design variants. The variants were introduced into a statistical energy analysis (SEA) model for the computation of airborne noise transmission of the vehicle with respect to power-train noise. Thanks to these SEA models, the medium and high-frequency interior Sound Pressure Level for thousands of variants was evaluated, to allow the selection of the best performing solutions in a Pareto plot. The best performing variant, providing a weight saving of about 4 kg, was realized with a tool designed specifically for this purpose and then it was evaluated in terms of transmission loss with and without all accessories (including the instrumentation panel) and compared to the original mass-spring solution. According to the positive achievements of these tests, the new solution was also mounted in a vehicle and compared to the original solution in terms of airborne acoustic transfer functions and road subjective and objective NVH performance.
Optimization of a dash "hybrid" insulator-absorber based on pareto analysis of SEA simulation results
2011
29 Seiten, 20 Bilder, 24 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
Acoustical Design of Vehicle Dash Insulator
British Library Conference Proceedings | 2011
|Acoustical Design of Vehicle Dash Insulator
SAE Technical Papers | 2011
|