The Research Of The Manipulation Of Acoustic Directivity Based On Inhomogeneous Materials

In the past decade,acoustic metamaterials have been widely concerned because of their special material properties.In the process of designing acoustic metamaterials,the design of metamaterials is basically based on the assumption of periodicity.The influence of structural periodicity on acoustic propagation has been widely studied in the field of metamaterials.However,up to now,there are few studies on aperiodic acoustic materials.In fact,periodic structure is a special case of aperiodic structure,but it is not necessarily the optimal distribution.On this basis,through theoretical derivation and simulation,this paper analyzes the acoustic propagation performance of aperiodic metamaterials.According to different application scenarios,the optimal performance of non-uniform impedance of the super structure material has been designed,and better control effect has been obtained.In the first chapter,we review the research background and practical application of acoustic metamaterials.The development of acoustic metamaterials in nonlocal effect,multiple scattering and fluid solid coupling in recent years is introduced.The main contents of this paper are summarized.In the second chapter,the radiation resistance is regulated by carving uneven grooves on the baffle.Through the analysis of diffraction effect and multiple scattering,the optimal groove distribution is inferred and verified by simulation.In addition,this chapter also discusses the inheritance relationship between this design method and the traditional soft boundary design method.In the third chapter,the free control of beam is often subject to the coupling of amplitude and phase.In this chapter,the coupling of amplitude and phase of transmitted sound wave is released through the optimal distribution of side branch.Different from the traditional side branch pipe in the straight pipe,the amplitude and phase are decoupled by adjusting the lateral position of the side branch pipe in the straight pipe,so that the amplitude change is as small as possible in the process of phase change.In the fourth chapter,the influence of nonuniform impedance on directivity and sound distribution is discussed,and an attempt is made to find the optimal impedance distribution.The fifth chapter reviews the content of the paper,and makes a proper outlook for the follow-up work,hoping to carry out more in-depth research.