Numerical Calculation Of Sound Absorption Of Artificial Periodic Structures And Its Application Of Noise Reduction In Vehicles

With the development of science and technology,machines gradually replace human beings to participate in all aspects of production and manufacturing.However,the noise generated during the operation of machinery and equipment not only affects the control accuracy of the equipment,but also harms people’s physical and mental health.Therefore,noise control has increasingly become a hot topic.As of 2017,China’s vehicle population has exceeded 300 million.With the development of the market and industrial upgrading,people have not only satisfied with the convenient traffic brought by vehicles,but have gradually begun to pursue the comfort of vehicle driving.The car’s NVH(noise,vibration,harshness)is the core technical issues of improving passenger comfort.In this paper,based on the traditional Helmholtz resonant cavity structure(HR),the acoustic characteristics of one-dimensional and two-dimensional periodic HR are studied,and a new two-dimensional periodic structural plate that can be used for car noise reduction is designed.The main research content of this article is as follows:Firstly,the lattice theory and Bloch theory are introduced.The reasons for the band gap generated by the periodic structure are analyzed.Through an example,the steps of calculating the bandgap,response spectrum and sound pressure distribution diagram using the finite element software COMSOL are introduced.It laid the theoretical foundation for the study of the acoustic characteristics of the periodic structure.Secondly,a single HR,series-parallel HR and one-dimensional periodic HR structure are simulated and calculated respectively;the sound absorption characteristics and the local effect on the acoustic energy of the one-dimensional periodic HR structure with point defects are analyzed;and a mosaic film structure is designed.The HR structure,coupled with the acoustic characteristics of the two structures,can produce more sound absorption peaks at low frequencies without increasing the structural mass and volume.Analysis of acoustic characteristics of two-dimensional HR periodic structure.Thirdly,based on the fact that the HRs with the same volume and different geometries have different resonance frequencies,a thin and light broadband sound-absorbing panel is designed for HR cycles of different geometries.The shapes are regular and can be combined with each other.Through simulation and experiments,it is verified that this two-dimensional periodic structure has good sound absorption characteristics.The application of artificial periodic structure in vehicle.Finally,the two-dimensional periodic HR structure is placed on the roof of the car,and the changes in the sound pressure level curve of the driver’s head before and after adding the interior trim and periodic structure are analyzed,confirming that this periodic structure can reduce the mid-high frequency noise in the vehicle.This paper systematically studies the acoustic characteristics of the periodic structure and designs a new type of wide bandgap periodic plate,which provides a new method for noise reduction in the car.