Passive/Active Acoustic metamaterials
Within the last years, an increasing number of studies have been carried out in the field of acoustic metamaterials. These artificial composite materials aim at achieving new macroscopic properties, like negative refraction, that are not readily present in nature. In analogy to electromagnetics, where such concepts are already more mature, a novel concept of artificial acoustic transmission line has recently been reported, which presents such artificial behavior. In this presentation, the design of the proposed transmission line is presented and a validation is made with the help of a finite element model. Moreover, these results are compared to a usual circuit description of the problem. One cell and 10-cell long structures are implemented in Comsol Multiphysics® and confirm the good performances of the different models, in terms of dispersion diagram, Bloch impedance, as well as reflection and transmission coefficients. In parallel, the progress made in the field of acoustic acoustic impedance control pave the way to a new class of acoustic metamaterials, in which the different elastic membranes could be actuated so as to exhibit variable acoustic impedance, thus controllable mass density and bulk modulus.