Acoustic Experimental Modal Identification And Simulation Modeling Based On Adaptive Filtering

China's railway development as the sun is just rising,there is no doubt that the railway has become a major economic artery,an important infrastructure and mass transit in our country.However,as the train structure tends to be rapid and complicated.The noise and vibration of the train brought about by the train have gradually been paid attention to by the public.There are structural modes and acoustic modes in a closed room.When the air in the car is compressed,the volume of the air will change and result in a higher impedance.The cavity and structure vibration in low-frequency has great coupling effect,in external excitation the coupled modes of the structure and the cavity will produce higher pressure fluctuations at low-frequency,this is booming noise.Controlling the coupling of acoustics and vibration modes is an important means to eliminate booming noise,so it is essential to obtain accurate acoustic modal.Acoustic experimental modal were carried out in high speed railway cavity on the High-speed train test rigs for fundamental research.Using the audio console of the platform to provide sine sweep signal,NI-USB6255 data collector and microphones are important components of the acquisition system.meanwhile,64 sound pressure measuring points are arranged in total,and the longitudinal,transverse and vertical sound pressure signals of all the measured points are tested.In the matlab writing a program of LMS adaptive filter is used to denoise the acquisition signal,and getting satisfactory sound pressure signals.Using PloyMAX algorithm module of LMS test lab to extract the car acoustic modal frequency and modal type parameters.The modal assurance criterion of the modal frequencies of each order can prove the reliability of the parameters,the identified vehicle acoustic experimental modal frequencies and modal shapes,they will serve as the basis for modeling and simulation of calibration.By modifying the simulation model repeatedly,the simulation model is established when the error between the acoustic modal frequency of the simulation model and the acoustic experimental modal frequency is controlled within 15%.Combined with the modal parameters of the structure,the prediction can be achieved and the resonance of the modal frequency of the structure and the acoustic modal frequency can be avoided,which provides a reference for the study of low frequency noise control in high speed train.