Based On OPAX Method Analysis Of Noise Transfer Path Of Interior Structure

The transfer path analysis method is a test-based analysis method.When a vehicle is running,the engine vibration,intake and exhaust system noise and other incentives radiate to the passenger compartment of the vehicle through the body structure and air,which greatly affects the comfort of the driver and passengers.Simultaneously,the interior structure noise is the main interior noise.This paper uses the OPAX method to identify the main structure noise sources in a vehicle,and get the interior structure noise source.Based on the basic theory of OPAX method,the least square method is used to estimate the transfer function,and the single degree of freedom mount model is used to identify the working load,so as to calculate the contribution of each structure transfer path to the interior noise and fitted value of OPAX.Taking a domestic SUV passenger car as an example,the vibration acceleration signals of left mount,right mount,rear mount active and passive side positions and the noise pressure data of air intake position,exhaust position,driver’s right ear position,codriver’s left ear position and rear seat central position are obtained through the test.Then convering spectrum of working condition data and calculating the constant coherence function and partial coherence function respectively.Through the partial coherence analysis,draw a conclusion that the main influencing factors of the vehicle interior noise are the vibration of the engine mount system under constant acceleration condition.In other words,the interior structure noise is the main interior noise.The mount system vibration acceleration and the interior noise pressure are obtained by direct measurement.The interior noise pressure is divided by the mount system vibration acceleration to obtain the system frequency response function of the structure transfer path.Based on the collected working condition data to analyze orders and get the order slice data.Using the order slice data and the system frequency response function data,the OPAX model is established to identify the structural load,obtain the dynamic stiffness of each structure transfer path,then calculate the contribution component,analyze the contribution result,the structural noise source in a vehicle is identified as the vibration of engine right mount.Comparing partial coherence and OPAX analysis conclusion,both of them are consistent,the conclusion is reliable.