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Two structure-borne and two airborne paths were measured on 99 “identical” Isuzu RODEOs and 57 “identical” Isuzu pickup trucks. Significant effort was made to control measurement variability but not environmental (climate) variations. A record was kept of the tests of a reference vehicle over the variation of environmental factors. The frequency response functions (FRFs) of the reference vehicle varied by approximately 2-4 dB over the frequency range 0-500 Hz for the structure-borne paths and over 0-1000 Hz for the airborne paths due to measurement and environmental variations. The FRFs of the fleet varied by as much as 5-10 dB over the same frequency range. In this paper, the vehicle tests are described. The reference and the fleet data are shown in raw form. Reduced data and implications of the results are also discussed.

The mobility modeling technique is applied to the structure-borne noise path through a vehicle suspension. The model is developed using measured FRF data taken on the isolated components of the suspension and body structure of a midsize sedan. Several important modeling issues of suspensions are resolved. It was determined that multiple degrees of freedom are required to model the coupling at joints between the suspension and body structure. The investigation also demonstrated that bushings should not be included in the measurements used to develop these models and should be added later using simplified bushing parameters. The importance of transfer mobility information between the various suspension attachments was also investigated. The agreement between the mobility model predictions and the measured FRF data for the overall system is better than similar data published in the literature to date.

A feedback controller bas been developed using robust control techniques to control the sound radiated from turbulent flow driven plates. The control design methodology uses frequency domain loop shaping techniques. System uncertainty, sound pressure level reductions, and actuator constraints are included in the design process. For the wind noise problem, weighting factors have been included to distinguish between the importance of modes that radiate sound and those that do not radiate. The wind noise controller has been implemented in the quiet wind tunnel facility at the Ray W. Herrick Laboratories at Purdue University. A multiple-input, multiple-output controller using accelerometer feedback and shaker control was able to achieve control up to 1000 Hz. Sound pressure level reductions of as much as 15 dB were achieved at the frequencies of the plates modes. Overall reductions over the 100-1000 Hz band were approximately 5 dB.