Composite Acoustic Array Based On Acoustic Metasurface

In the field of acoustics,the design and construction of artificial structures enables such structures to have special functions that are not possessed by natural materials,so as to achieve the purpose of effectively manipulating acoustic waves.Such artificially manufactured materials are called acoustic metamaterials.In recent years,acoustic metamaterials(acoustic artificial structures)have developed rapidly.Acoustic metasurfaces with a thin subwavelength structure are an important branch of acoustic metamaterials.Based on the generalized Snell's law,it can achieve extraordinary manipulation of the wavefront.Compared with the traditional three-dimensional acoustic metamaterials,it has many advantages,such as small size controlling large wavelength sound waves,easy integration,and strong ability to control the sound waves.The active metamaterials has an active control unit that can provide energy or give feedback to the acoustic system.This process is controllable.It has broken the limits of passive,linear,and time-invariant properties of acoustic materials,and improves the effectiveness of metamaterials in applications.At the same time,acoustic arrays can also perform efficient manipulations of acoustic waves,and have always been a research hotspot in acoustic applications.Base on this,we present a new broadband acoustic composite PA,which can form a special beam and accurately determine the direction of the sound source,by combining active metamaterials,metasurface and conventional acoustic PA.The first chapter is an introduction.It mainly introduces the research background and progress of acoustic metamaterials,and some theories related to acoustic metamaterials.In the second chapter,we first introduce the generalized Snell's law,and then introduce the research progress of the current acoustic metasurface in the following three aspects:1.Folded structure type metasurface;2.Membrane metasurface;3.Broadband subwavelength corrugated surface.In the third chapter,we first briefly introduce active acoustic metamaterials based on previous work.Based on previous work,we design a composite broadband subwavelength active acoustic array that can be used to form special beams and determine the directivity characteristics of the source.The generalized Snell's law of refraction about acoustic metasurface and the classical acoustic PA theory are applied to interpret the internal physical mechanisms of the active tube array.The active tube array is theoretically proved to be a dispersionless acoustic control structure.The numerical simulation results and the experimental results are in consistent with the theoretical expectations,demonstrating the effectiveness of the active acoustic array.The fourth chapter is the conclusion and the outlook for the future work.