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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 application of SEA (Statistical Energy Analysis) to the sound package design for a convertible is presented. SEA modeling was used optimize the soft-top construction and the acoustic insulation in the top-stack area (where the soft-top is stored) which were shown to be important transmission paths for tire noise. Correlation between measurement data and predictions from the SEA model is presented and good agreement shown. It is concluded that SEA can be applied to determine the special sound package requirements for convertible vehicles.

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.

When characterizing absorption in vehicles, a knowledge of the in situ performance of the acoustical absorbers is often desired. To measure this is a relatively easy task in a large diffuse sound field. However, inside a vehicle where the sound field is not diffuse, the measurement is more difficult. Impulse and interrupted noise techniques have been used to measure absorption inside cavities with extremely short reverberation times. Among several difficulties associated with these techniques are the response time of the filters and the influence of the averager in the instrumentation. In many cases, these limitations make these traditional techniques impractical for use in a vehicle. With the advent of modern digital signal processing, however, there are a number of other readily accessible techniques that are more useful.