Research On Simulated Operational Path Analysis For Vehicle Interior Noise Source Separation

Noise,Vibration,Harshness(NVH)performance is closely related to the driving comfort of vehicle,and is also a key indicator to measure the vehicle quality,the level of development,design and manufacturing of vehicle companies.Accurate identification of the main vehicle interior noise sources is the basis for noise control and sound quality optimization,which has always been an issue that has been highly valued in the NVH research.Transfer Path Analysis(TPA)is an important way to solve this problem.The load-response type TPA represented by the classical TPA method has high accuracy,but when measuring the frequency response functions,it is necessary to remove the active component and adopt a specific excitation system,resulting in a cumbersome,inefficient and costly experiment processes.The response-response type TPA represented by the Operational Transfer Path Analysis(OTPA)method has high efficiency,but it cannot guarantee the accuracy of the separation of vehicle interior noise sources,especially when related sources acting on the system at the same time or there is a strong coupling between transfer paths.Under these conditions,the transmissibility matrix will be severely deviated from the real ones.This dissertation aims to solve the problems of the classical TPA method(Load-response type TPA and response-response type TPA)and propose an improved TPA method for separating of the vehicle interior noise sources,which is named as Simulated Operational Path Analysis(SOPA)method.SOPA method solves three major problems of response-response TPA method for multi-input system which are path cross-coupling,related excitation input,and transfer path omission.TPA adopting the SOPA method offers high accuracy and efficiency,simultaneously.Through theoretical analysis,bench experiments and real-vehicle testing,the effectiveness and convenience of the SOPA method have been proven.The quick separation of interior noise sources and accurate evaluation of transfer paths in a passenger car have been realized,which provides a basis for noise control and sound quality optimization.The specific research points are as following:(1)Establishing SOPA method.Acoustic load and structural load are synthesized through external sound sources and external forces under operating conditions.The transmissibility of each transfer path is measured separately,thus physically decoupling the multi-input system into multiple single-input systems.Based on transmissibility between reference points,an inverse transmissibility matrix method is proposed to eliminate crosstalk of reference response signals and background noise.A SOPA method for separation of vehicle interior noise sources is proposed,and the feasibility of this method is verified through experiments.(2)Transfer Path Analysis of the of the vehicle interior structural-borne noise and air-borne noise under simulated conditions.The simulating methods of the excitation source loads such as the engine structure-borne noise,the intake and exhaust noise,the structure-borne and the air-borne road noise are studied.Based on the simulated loads,the transmissibility between reference points and target point are measured,and the accuracy of the transmissibility is verified experimentally.By adopting the inverse transmissibility matrix method,the crosstalk in the reference signal and background noise are eliminated.The SOPA models of structural load and acoustic load are established,and the synthesized responses are compared with the measured ones,which verifies the accuracy of the SOPA method when it is used in the TPA of the vehicle interior structural-borne noise and air-borne noise.(3)Research on the separation of vehicle interior noise sources based on SOPA method.Combining the transmissibility measured by the simulated loads and the pure reference signal obtained by the inverse transmissibility matrix method,a SOPA model specially for the analysis of the entire vehicle transfer path is established,which realizes the separation of vehicle interior noise sources.Comparison of the SOPA method and the classical TPA method in separating the vehicle interior noise source and conclusions are drawn as: the SOPA method does not need to remove the active component such as the engine,suspension system,etc.,nor does it need to use hammer and micro-volume sound source to measure the frequency response functions.The load of each excitation source under operating conditions for calculating transmissibility between each transfer paths can be simulated by only traditional hammers,vibration exciters,and loudspeakers.In addition,the required reference sensors are less than one-half of the classic TPA.Compared with OTPA method,even though the SOPA method need a little bitter complicated experimental equipment and is slightly less efficiency,it can significantly improve the accuracy of the transfer path analysis.Considering the experimental equipment requirements,the complexity of the experimental procedure,the efficiency and accuracy of the experiments and other factors comprehensively,the SOPA method has obvious advantages.Combining the SOPA method with the above-mentioned traditional method can demonstrate the advantages of SOPA in considering both accuracy and efficiency simultaneously.The research provides a basis for noise control and sound quality optimization,and has important theoretical significance and engineering application value in the improvement of automotive NVH performance.