DRE NVH Contribution Analysis of Vehicle Cavity Fillers - NVH Target Setting Process 2009-01-2169

The goal of this study is to measure the Noise, Vibration and Harshness (NVH) performance of passenger vehicle cavities under different drive conditions. Until now, little attention has been given to the impact of NVH performance of cavity fillers with respect to the driver's perception. To further understand this phenomenon, a four door sedan was instrumented with several microphones placed within different vehicle cavities. After instrumentation, the vehicle was tested under various road conditions; cruise, idle, street run, rough road and wide open throttle. The resulting data shows that there is a substantial noise presence in the hinge pillar and lower rocker cavities for all test conditions. The data also provides a means to rank the importance of the sound contribution of each vehicle cavities with respect to other cavities.

To understand the NVH contribution of individual cavities to the driver's perception, the vehicle was placed inside a semi-anechoic chamber. The goal was to compute the transfer function of each cavity with respect to the driver's ear (DRE). The individual transfer functions could have been calculated by placing the random noise generator within each cavity while measuring the response at the DRE. This technique would have required several iterations of moving the noise generator from cavity to cavity. However, using the reciprocity concept, the noise generator can be placed at the DRE and the responses at all cavities can be measured simultaneously. Finally, having the road data along with all transfer functions, the relative importance of each cavity was determined with respect to the driver's ear.

This methodology would enable vehicle manufacturers to understand the importance of cavity fillers to the vehicle's overall NVH performance. This technique would also help to optimize the application and provides NVH target setting goals for the vehicle cavity fillers.