The Analysis And Improvement Of A Certain Vehicle About Pass-by Noise And Exhaust Noise Problem

In the past centenary, the automobile industry has been developed rapidly, people’sliving has been changed with the development of social productivity owing to cars. Withthe improvement of living standard and awareness of environmental protection forpeoples, more stringent requirements for the noise level, as well as car’s comfort, is pur-suit for modern people. The latter becomes an important factor to evaluate the automo-bile brand.In automotive engineering applications, the vehicle is generally chosen as an re-search object to analyze the NVH characteristics for automotive. However, auto systemconsists of a huge number of components with a very complicated structure. Hence, inpractical engineering, it is usually divided into many subsystems, such as power trainsubsystem, intake and exhaust subsystem, then each subsystem was analyzed respectively.Also we are able to analyze the NVH characteristics provoked by a specific excitationsource in certain conditions.The sources of vehicle noise consists of two categories: one kind is induced by thevehicle itself, such as the intake noise, exhaust noise, engine radiated noise; the otherkind is induced by the friction between the vehicle and its contact body, such as tire-roadfriction noise, wind noise excitation et al. Since the regulations on vehicle noise emissionlimits are becoming more strict, it’s necessary to study on automotive noise. Among them,The noise source of exhaust system includes: airborne noise, impulsive noise, radiationnoise, air friction noise. Exhaust noise is a major noise source for automobile, hence, itmakes great sense to analysis and test exhaust noise in order to reduce the noise level forautomobile.In this paper, some theories and methods for the R&D process of the NVH perfor-mance of a certain vehicle is introduced, in order to describe the research status and de-velopment trend of exhaust noise and pass-by noise. Then, focusing on the obvious ex-haust noise problem, which is contributed more noise to the vehicle interior noise at idlespeed and band3full throttles speed, and aiming at the problem that testing value of theoutside noise sound pressure level when accelerating exceeds of the regulatory require-ments, the vehicle is chosen as the research object to be studied and tested. With com-paring the testing results of some samples in different state, the reason for over exhaustnoise was cleared. Hence, some corresponding strategy on improving the exhaust struc- ture was proposed, which successfully proved to reduce the vehicle’s exhaust noise levelto the desired value. Subsequently, by comparing the test data of the exhaust noise in ac-celeration with the one of the benchmarking car, it is found that due to the exhaust ordernoise, the car’s exhaust noise data could not meeting standard. Moreover, by tracking theengine speed to lower the torque converter lockup speed, the exhaust radiated noise ofthe vehicle was successful reduced to meet the regulatory requirements.The proposed methods and improvement strategy are originated from practicalprojects, it makes reference value to solve similar problems for other vehicle NVH is-sues.