The Transmission Of Sound In Waveguide Complex

As a carrier of energy,acoustic wave plays an important role in the fields of physics,medicine,military affairs,information transport and so on.The anomolous control of acoustic waves has great significance to the understanding of physical mechanism and industrial application of acoustic functional materials,such as the negative refraction / reflection of acoustic waves,the collimating and focusing,the super-resolution imaging,the acoustic cloaking,the topological transmission and so on.As a special kind of acoustic structure,acoustic waveguide can control the propagation of acoustic wave along the axis of the waveguide in the form of a plane wave and suppress the propagation of other directions.As a kind of acoustic functional materials,acoustic waveguide periodic structures have received much attention of researchers.The special coupling modes between the waveguide have a rich physical connotation.Due to the mutual coupling between the evanescent waves in the waveguide array,the wave is disturbed in the propagation process,and the effective information cannot be transmitted.The coupling equation of waveguide array are derived,by using governing equation of acoustic,combining with the transfer matrix method and the boundary conditions.Based on the analytical method of eigenmode analysis and projection band calculation,transmission characteristics without diffraction and distortion are detailedly studied for the acoustic strip-type array and circular-type array.The main innovations of this paper are as follows:(1)A one-dimensional five waveguides strip array structure is designed.The existence of supermodes in the five waveguides system is demonstrated experimentally.Based on the eigenmodes of theoretical analysis,when the incident wave satisfies the intrinsic excitation conditions of the waveguide array,namely the input pressure distribution of each waveguide equivalent to eigenmode distribution,the amplitude and phase relationship of acoustic wave is robustly transmitted in the waveguide array without any distortion,and the total pattern of supermodes strictly equal to the number of waveguide in waveguide array.The results of numerical simulation and experimental measurements show that the formation of the supermodes only require the incident wave to satisfy the intrinsic excitation condition of the waveguide array,but it is independent of the operating frequency of the incident wave.It is also found that the transmission wavelength of acoustic supermodes in the waveguide array increases with the increase of the mode order and decreases of frequency from the numerical simulation and experimental measurement.(2)A two-dimensional waveguide array with the broadband low loss transmission is designed,which has the characteristics of anomalous Floquet type topological insulator.Given the previous design of an anomalous Floquet type topological insulator in our group,which is based on the coupling of the metamaterial resonant ring,we use directional coupler to connect two adjacent resonant rings to enhance the coupling between the resonators.This kind of structure is relatively simple,and the frequency of directional coupling is very wide.The results of theoretical calculation and numerical simulation show that the transmission of the basic unit is very high,and the propagation loss of a single cell is less than 2% for the topological edge state.The frequency range of the topological state can occupy about 84% of the whole band structure,and the coupling efficiency can reach 97% in 4.8kHz ~7.0kHz.And the topological edge states are topologically protected and waves can be transmitted without distortion at the corners and the boundary of the defect.