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In a traditional NVH development process, the realization of the targeted vehicle acceleration sound quality can be a highly laborious and costly process involving the creation and evaluation of multiple iterations of prototype parts. Consequently, development engineers are limited by long prototype part fabrication times while key product decision makers have to often accept the “in-process” sound quality due to aggressive program timing milestones and escalating program costs. The NVH simulator provides an alternative approach that is potentially more efficient in terms of reducing program timing, reducing development and prototype costs and improving the end-product sound quality. This paper presents the case of a V6 vehicle under development whose acceleration sound quality needed improvement. The NVH simulator was used to determine the key contributors that lead to the sound quality of the targeted vehicle.

The fuel economy benefits of Continuously Variable Transmission (CVT) technology have led to a steady growth in their adoption since the 1990's that is likely to continue despite the competition from Dual Clutch Transmission (DCT) & Automated Manual Transmission (AMT) technology. Even though CVTs provide a smoother driving experience due to their “shift-free” operation, general market feedback indicates some level of consumer dissatisfaction in the area of acceleration sound quality. This is particularly evident in the sub-compact and compact vehicle segments that feature small four cylinder engines with cost/weight limited sound packaging. The dissatisfaction with the acceleration sound quality is primarily linked to the non-linear relationship between engine RPM and vehicle speed that is inherent to CVTs and is often referred to as “rubber-band” feel.

The advantages of hydraulic mounts over conventional elastomeric mounts for NVH refinement are well known, particularly in the area of engine and suspension mounts. Recently, hydraulic mounts have been successfully employed as body mounts between the frame and cab, principally to control freeway hop in pickup trucks. Due to their ability to provide increased damping at small displacements, hydraulic body mounts also have good potential to reduce smooth road shake. This paper documents the reduction in smooth road shake performance of a full size pickup truck. Hydraulic body mounts tuned to the frequency of the smooth road shake sensitivity area were added to the rearmost cab mount location. Both tire-wheel balance and uniformity were set to the highest production level specification allowed and the effect of hydraulic cab mount was measured experimentally during smooth road driving at medium to high speeds.