Analysis On Contribution Of Interior Noise And Vibration Transfer Paths In Metro Based On OTPA Method

With the rapid increase of the urban population and the amount of private cars,the urban road traffic is under tremendous pressure which leads to the rapid development of the metro transportation,due to its punctuality and large capacity.The vibration and noise in metro vehicle,as important indicators of riding comfort,its criteria has become more and more strict.The metro interior noise control must be considered from the three factors of noise,it is particularly important to find the main transfer paths and sources of excitation in the vehicle.In this thesis,the method of combining test and signal analysis is adopted to carry out the research on the identification of noise sources inside the vehicle,and the influencing factors of interior noise as well as the contribution of vibration transfer paths based on the principles of sound source identification and operational transfer path analysis(OTPA).In order to provide reasonable and effective solutions to the problems of vibration and noise for metro vehicles.The main research contents of the thesis are as follows:(1)For several commonly used transfer path analysis methods,their advantages,disadvantages and scope of application are briefly introduced,the basic principles of the OTPA method are elaborated at mean time.The shortcomings of traditional contribution evaluation method are then theoretically proven and another method based on amplitude and phase is proposed.(2)Based on the basic principles of the sound source identification,the sound source identification test in metro vehicle is carried out.The main source areas of interior noise for different frequency bands are determined while the metro vehicle operating at a typical speed level.The results show that in the frequency range of 125～630 Hz,the floor is the main noise source area,while for the frequencies above 800 Hz,the rear roof becomes the main contribution area(3)Based on the vibration and noise field test,the effects of the running speeds,operating directions,air conditioning status and body materials on the interior noise of the metro vehicle are analyzed.The results indicates that the operating speed has a greater impact on the interior noise,other factors are less influential to in the noise inside the vehicle the changes caused by which are below 2 d BA.(4)By using the contribution evaluation method based on amplitude and phase,the conclusion for the metro vehicle running at 60 km/h is drawn,that in the significant frequency range of the interior noise of metro vehicle,300～800 Hz,the transfer path with the largest contribution in the secondary suspension transfer paths is the vertical direction of anti-roll bar and the second largest is the longitudinal direction of the air spring.The largest contribution path in the primary suspension transfer paths is the longitudinal direction of the shock absorber,followed by the longitudinal direction of the axle box arm.A reasonable optimization scheme to reduce the response of the target point is proposed according to this result,which will provide a reference for the subsequent low-noise design of similar vehicle.(5)For the crosstalk problem in the transfer path measurement,a crosstalk cancellation method based on frequency response function matrix is studied in order to obtain a more realistic vibration source signal.At the same time,Cholesky decomposition method and least square method are also introduced to reduce the measurement error influence and improve the solving equation solving accuracy.The simulation of crosstalk cancellation is performed,to compare and analyze the data before and after crosstalk cancellation.The simulation results show that the crosstalk cancellation method can achieve preferable optimization.