Influence Law Of Minivan Body Structure On Low Frequency Interior Noise

With the development of automobile industry and the continuous improvement of the people’s living standards,the vehicle,as a traffic tool,is not only concerned with the dynamics and economics of the vehicle,but also concerned with the ride comfort.During the driving process,the status of driving at low speed appears frequently,and the noise of low frequency at low speed has an effect on drivers and passengers obviously.Therefore,it is a great engineering significance to study the low frequency noise of the vehicle.The low frequency booming noise is structureborne,and it is transferred to the interior vehicle through the chassis and body,and formed in the vehicle.However,the factors which contain the parts of vehicle and the boundary involved are complicated,it is difficult to control the interior noise of vehicle with a universal and stable method.Therefore,this paper investigates a minivan with the target of controlling the interior noise.Through the study of the noise source and the noise transfer path,the main noise contribution panels of vehicle can be found and controlled to reduce the noise of vehicle and improve the ride comforts of drivers and passengers.The specific research contents are composed of the following aspects(1)Under multi-point excitations,the statistical screening classification method of noise transfer function(NTF)are studied.With the models of minivan body and cavity,the interior of minivan can be obtained by the method of noise transfer function.The method of statistical screening classification is applied to get the classification and recognition of noise formed under different excitation conditions,and the distribution condition of interior noise could be obtained under multi-point excitations.Then,the noise transfer conditions of critical noise frequency points are analyzed and classified to improve the efficiency of analysis.(2)The inner relationship between minivan body panel,modal and interior noise is studied.With the methods of panel participation factors(PPF)and modal participation factors(MPF),the interior noise of minivan are analyzed under multiple noise transfer conditions.The contribution factors of the minivan body panels and modal are obtained on the interior noise of minivan,and the results could establish the quantitative relationship between the above three aspects.It provides the basis to distinguish panel and modal effectively about the interior noise of minivan.(3)The modal changing characters are investigated on the important minivan body panels,and the influence law of key body structural parameters is obtained on the interior noise.Taking the body roof as the research goal,the rule of roof modal can be obtained through the changing of roof beads.With the methods of the damping adhesive,dynamic vibration absorber(DVA)and local structure optimization,the roof modal and stiffness rules are obtained and applied to reduce the interior noise.(4)The effect rule of body structure to the interior noise is simulated and tested.The single and combining optimization of the body panel are analyzed,and the effect situations are obtained,and it provides the basis to the design of minivan low frequency noise.In addition,the response surface methodology(RSM)is applied to study the relationship between the dynamic vibration absorber(DVA)mass parameter and the interior noise of minivan.It proves a direction to improve the effectiveness of the noise transfer function.By contrast,if the sound pressure level reduction of interior noise is only considered,the dynamic vibration absorber should be chosen as an effective measure.If the reduction of the sound pressure level and additional mass are both considered,the local stiffened bead can be selected.It provides some practical guiding significance to improve the modal of body structure and reduce the interior noise of minivan by the above analysis and tests.