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In this paper, a methodology is discussed to achieve cost-effective solutions for improving vehicle Noise, Vibration and Harshness (NVH) performance of a body-on-frame Multi-Utility Vehicle (MUV). The subject vehicle had objectionable levels of in-cab boom and gear rattle while accelerating in higher gears due to power-train and driveline excitations. Potential transfer paths which might be responsible for amplifying these phenomena were tracked using contemporary noise and vibration measurement techniques. Various modifications were evaluated to improve NVH performance under constraints of vehicle-packaging. An optimized combination of these modifications resulted in improvements in the NVH performance over a wide range of operating speeds with reductions of up to 10 dB achieved in firing frequency excitation, thus eliminating the objectionable boom and gear rattle from the vehicle.

In the automotive industry there are now several methodologies available to estimate the Combustion Mechanical Breakdown (CMB) of engine radiated noise. This paper compares the results of two different CMB analysis methodologies (multiple regression vs. coherence) performed on a HSDI diesel powertrain installed in an Engine Noise Test Cell (ENTC) and highlights the specific differences in the way each method defines combustion and mechanical noise.