The Cause Analysis And Improvement Of Whine Noise Of A Car At 50kph Speed

Transmission is one of the main noise sources of a vehicle. Controllingits noise level will directly affect the performance of the vehicle’s NVH.In addition to ensure that the transmission has good working performance,controlling its vibration and noise level has become one of the important indicators during its development. Based on a whine noise problem of a passenger car,this thesis analyzed and researched its reason of the formation and possible measures for the improve by experiment test and theory analysis method.This research work made an important engineering practical value for improving the design and the riding comfort of the passenger car.A car with a seven-speed dual clutch gearbox has a whine noise when it is going at a constant speed of 50km/h. On the condition of whine noise problem,this thesis firststudied and formulated the noise and vibration test plan, and tested the vehicle’s noise and vibration, then using frequency spectrum analysis to analyze the results of the transmission’s vibration test,and later on determine the frequency of the whine noise by the playback of the driver’s right ear noise after filtering, and using order tracking analysis to further evaluate the noise and vibration signals in order to confirm the source of the whine noise.Finally, it concluded that the driveshaft was the main transmission path of the whine noise by comprehensive analyzed all possible paths.In order to improve the whine noise in this working condition,this thesisstudied the method and theory to improve the whine noise. Considering that the model is already on the market, a reasonable approach is usedto improve the whine noise by optimizing the transmission path:choosinga dynamic vibration absorber to absorb the vibration energy of the driveshaft. It has a simple structure, low cost, and is easy to install. After comparing the test vehicle and subjective evaluation findings, this thesis concluded that the whine noise is improved significantly after assembly dynamic vibration absorber on the driveshaft of the vehicle.This thesis started from the mechanism of whine noise,and summarized a set of testing the transmission whine noise in engineering analysis, and achieved lower the whine noise of a passenger car while travelling at a constant speed of 50km/h.This research provides a method of engineering application value in improving the established passenger car’s whine noise and its riding comfort.