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A quiet passenger compartment is highly desired by today's customers. Vehicle design teams spend significant time and resources to minimize the vehicle's interior noise due to different exterior noise sources. Drive-by vehicles on the highways generate one of these noise sources. The objective of this study is to establish a correlation between customer's on-road experience due to drive-by noise and Noise Reduction Level (body transparency) tests conducted in a reverberation room. The average Noise Reduction Level (NRL) obtained in the reverberation room tests correlates (R2=0.89) with the peak loudness of on road tests. A sound quality listening study was also conducted to determine the most preferred NRL spectral distribution and its frequency range sensitivity.

The capability to drive NVH quality into vehicle frame design is often compromised by the lack of available predictive tools that can be developed and applied within the timeframe during which key architectural design decisions are required. To address this need, a new parametric frame modeling approach was developed and is presented in this paper. This fully parameterized model is capable of fast modal, static stiffness & weight assessments, as well as DSA/optimization for frame design changes. This tool has been proven to be effective in improving speed, quality and impact of NVH hardware decisions.

This paper describes experimental methods for simulating and analyzing road noise using an artificial road surface mounted to a chassis dynamometer. The nature of the relationship of road noise to road surface is discussed, including the nature of sound produced by the artificial surface mounted to the dynamometer. A method is described for converting the harmonics usually produced in a chassis rolls test into a continuous spectrum. This method also smoothes statistical fluctuations which arise due to the short length of road simulated. Dynamometer techniques are shown to be particularly effective in separating sound contributions from the front and rear suspension, and in separating contributions due to road surface and the tire tread.