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The optimization of acoustical properties of multi-layered materials used in the automotive industry requires a good understanding and characterization of the various component layers. This is a particular concern in the case of headliners where performance must be balanced with packing space demands. These composite structures when used with flexible urethane foams provide good stiffness and light weight, but their acoustic performance can be sub-optimal. Measurements undertaken with poro-elastic high airflow resistivity foams highlighted frame resonances which, if exploited, might significantly improve the acoustical performance of this system. A new modeling technique based on a pseudo-macroscopic description of the poro-elastic material in the framework of a four-pole network will be used to explain these frame resonances. This formulation exploits the electro-acoustical analogy in transmission line theory.

This paper discusses an analytical tool that has been developed to predict what types of interior sound package treatments may be necessary in a truck cab to meet a predetermined target sound level at the driver location. The steps that were taken to develop this tool involved a combination of experimental measurement and analytical based studies. Measurements were conducted to identify the acoustic strengths of the major noise paths through which sound travels from outside to inside the truck. These findings were then used to develop a sound package that reduced the vehicle interior noise to meet the target. Measurements were primarily made on a chassis roll dynamometer with final road verification to substantiate the dynamometer data. Data obtained from these measurements were also used in the analytical model that predicts the impact of various acoustics parts in the vehicle, and has the capability to optimize the sound package treatment in the vehicle.

The increasing complexity and competition in the car market pushes OEMs to simultaneously achieve both a lead-time reduction and a higher development process productivity. Therefore, car manufacturers are asked to significantly revise their development and production procedures, together with their suppliers who are co-designers vehicle-systems (seating, dashboard, lighting, etc.). Innovative CAD tools, such as parametric and associative (p/a), may significantly increase efficiency and effectiveness of design activities, through assisted procedures, automatic checking of constraints, avoidance of repetitive handle operations. By this way, p/a CAD tools may reduce the time requested for geometry description and modification, leaving the designer more opportunities for studying the design solution.