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A comprehensive investigation was carried out in order to develop the idle sound quality for diesel V6 engine when the engine development process is applied to power-train system, which included new 8-speed automatic transmission for breaking down the noise contribution between the mechanical excitation and the combustion excitation. First of all, the improvement of dynamic characteristic can be achieved during the early stages of the engine development process using experimental modal analysis (EMA) & the robust design of each engine functional system. In addition, the engine structural attenuation (SA) is enhanced such that the radiated combustion noise of the engine can be maintained at a target level even with an increased combustion excitation. It was found that the engine system has better parts and worse parts in frequency range throughout the SA analysis. It is important that weak points in the system should be optimized.

Gear rattle is generated basically due to the impacts of unloaded gear pairs in transmission. The rattle noise level is determined by two main factors, excitation level at transmission input shaft and rattle sensitivity of the transmission at that excitation level. In this work, (1) the transmission rattle sensitivity was measured and investigated (2) torsional vibration model of driveline system was developed to estimate the speed fluctuation at the transmission input shaft and to find some rattle improvement potential by tuning driveline components so that the speed fluctuation be minimized.