Research On Band Gaps Properties And Noise Reduction Performance Of Periodic Sound Barrier

The band gaps properties of periodic structures provided some new perspectives and ideas for vibration and noise reduction of engineering structures,and has been widely studied in vibration control.However,the study on how the band gaps properties of periodic structures be applied in noise reduction is rarely reported.This dissertation make in-depth research on band gaps properties of periodic sound barrier,and based on acoustic wave propagation characteristics,noise reduction performance of the fully enclosed sound barrier and semi-closed sound barrier are studied.1)In order to research on band gaps properties of periodic sound barrier,numerical analysis method and finite element method are adopted in this paper,Along with the orthogonal experiment design method and periodic structure theory,how the band gaps of the one-dimensional gas-solid periodic sound boarding is influenced by the density ? the sound velocity?the filling rate of the solid material and the lattice parameter are studied.2)In aspect of noise reduction performance of the periodic sound barrier,finite element method as well as acoustic-structure coupling method are adopted.How the noise reduction performance of the one-dimensional gas-solid periodic sound boarding is influenced by the density?the sound velocity and the filling rate of the solid material are studied.The results show that(1)The starting frequency and the cut-off frequency are significantly influenced by the density and the filling rate of the solid material.The sound velocity of the solid material has little influence on the starting frequency;(2)The starting frequency is greatly decreased with the increase of density of the solid material.At the same time,the cut-off frequency increases and the band gap broadens;(3)The lowest starting frequency is obtained when the filling rate of the solid material equals 0.6;(4)Because of Low frequency resonance,it is difficult to increase the noise reduction ability by adjusting the material parameters and structural parameters of the periodic sound barrier in low frequency stage;(5)The fully enclosed periodic sound barrier has better noise reduction ability than the single layer sound barrier with the same thickness,which can be improved by14 ~ 21dB;The semi-closed sound barrier has a better noise reduction ability than the single layer sound barrier with the same thickness,which can be improved by 3 ~ 6dB.