Helmholtz resonator based metamaterials for sound manipulation

Metamaterials are tailored artificial structures that received wide attention now a days due to their extraordinary properties like negative density, negative bulk modulus, negative permeability, negative refractive index etc.. Shape, geometry, size, orientation and arrangement of the basic units in metamaterials give them their smart properties capable of manipulating electromagnetic and acoustic waves by blocking, absorbing, enhancing, or bending waves to achieve benefits that go beyond what is possible with conventional materials. Acoustic metamaterial with Helmholtz resonators (HRs) is considered in this study. The behaviour of acoustic waves in the presence of array of Helmholtz resonators in series and parallel arrangement is studied numerically using finite element method. Series arrangement of Helmholtz resonators resulted in the extraordinary transmission of acoustic waves of certain frequencies and parallel arrangement resulted in the focusing of sound.