Research On Identification And Reduction Technology Of The Booming Noise In A SUV

At this stage,with the improvement of life quality,People's desire for comfort is also growing.As for automobile manufacturers,only by improving the comfort of the car can they stand out from the highly competitive market.This paper relies on the NVH performance improvement project of a SUV,using the method of simulation analysis,theoretical derivation and experimental verification to deal with the booming when the engine working at the range of 2700r-3100r/min.This article first introduces the various NVH diagnostic methods commonly used in prototype car testing,then conduct a basic test on outdoor asphalt pavement.By comparing the sound pressures of front and rear row,can draw a conclusion the source of the problem is mainly in the front.Afterwards,a third-gear wide open throttle acceleration test is performed on the hub in the vehicle's semi-anechoic chamber.Using order analysis to determine problem frequency during the acceleration process,and then shield the air intake system with "Separate Operation Elimination Method",the booming disappeared,this indicates the booming is caused by air intake system.The intake system noise may be caused by the air filter when it's structural mode is excited or the dynamic stiffness of the air filter installation is insufficient.For this reason,it is necessary to make the structural analysis of air filters.After a brief introduction of modal theory,making a structural analysis of the intake system with the help of HyperMesh and Nastran,and then get the top 10 modal frequencies.The LMS Test.lab test system was used to test the input point inertance of the air filter installation.Calculate the acoustic modality of the pipeline with the help of Virtual.lab.By analyzing the structural modal frequencies of the air filter,can get that it is less likely the Acoustic vibration coupled resonance of the air intake system will occur.Lastly,Test the transmission loss of air filter in a standing wave tube and focus on the transmission loss corresponding to the booming frequency.Through the above-mentioned simulation and experimental analysis,the problem of noise and vibration coupling and installation dynamic stiffness of air filter is eliminated.The booming in the car is mainly due to the existence of 97 Hz silencer passing frequencies in the air filter.In response to this kind of problem,many measures have been taken to solve the problem of installing silencer components in engineering.For this reason,this paper introduces the common silencer elements in the air intake system.The principle of the respective muffler is introduced with the expansion muffler and the Helmholtz resonator as an example,and the influence of various structural parameters on the noise attenuation performance of the components is analyzed.Finally,the Helmholtz resonant cavity was designed according to relevant theories and make a prediction of transmission loss through Virtual.lab.Then the hand-manufactured prototype was installed on the prototype car for hub and outdoor testing.Finally the validity of the measures was confirmed by comparing the front and rear sound pressure data in the car,and the accelerated booming of the prototype car was solved.