The Theory And Design Of Acoustic Metamaterial

In the past century, the absorption of acoustic waves has been extensively studied due to numerous practical applications such as noise control, reverberation design, etc.Recently, the emergence of acoustic metamaterials has provided new opportunities for advanced control of sound absorption.Acoustic metamaterial is a periodic artificial composite structure composed of different elastic modulus and mass density. By designing proper locally resonant structures, acoustic metamaterials can exhibit almost arbitrary effective parameters, including negative mass density, negative bulk modulus, negative shear modulus, double-negative, and many unusual density and moduli configurations.Metamaterials with such unusual parameters, not only give rise to novel applications such as super and hyper lens, cloaking and illusion optics, but also can enormously enhance the absorption of acoustic waves. In this work, we analyze the intrinsic physical origin of such complex dynamic mass density, and we propose a theoretical approach to calculate the complex dynamic mass density for acoustic metamaterials. By numerically investigating transmission properties and realizing coherent perfect absorption.Moreover,Our work provides a feasible approach to realize broadband perfect absorption of elastic waves in ultra-thin films.The dissertation is organized as follows:In the chapter one,We briefly introduced the research progress of photonic crystals,photonic crystals, electromagnetic and acoustic metamaterials.In the chapter two,Complex dynamic mass density in acoustic metamaterials,we analyze the intrinsic physical origin of such complex dynamic mass density, and we propose a theoretical approach to calculate the complex dynamic mass density for acoustic metamaterials.In the chapter three, The theory of perfect absorption for elastic waves. We analyze the mechanism to achieve broadband perfect absorption for elastic waves by using an ultra-thin film. Based on the transfer matrix theory, we find two types of ultra-thin films with such possibility.