We present theoretically a type of one-dimensional _1D_ structured ultrasonic metamaterial that exhibits a forbidden band where both the effective dynamic density and bulk modulus are simultaneously negative. The material consists of a 1D array of repeated unit cells with shunted Helmholtz resonators. The transmission coefficient, wave vector, negative dynamic density, and modulus are determined by means of the acoustic transmission line method (ATLM). The double negativity in the effective dynamic density and bulk modulus is an acoustic counterpart of negative permittivity and permeability in the electromagnetic metamaterials. The double negative band is ascribed to the localresonance. In order to confirm the ATLM results, we further calculate the field intensity, phase distribution, and transmission coefficient using the finite element method. In addition, the influences of some essential geometric acoustic parameters on the transmission properties, such as periodic constant L, are also discussed.

The authors demonstrate that a class of ultrasonic metamaterial, which is composed of subwavelength resonant units built up by parallel-coupledelmholtz resonators with identical resonant frequency, possesses broadocally resonant forbidden bands. The bandwidths are strongly dependent onhe number of resonators in each unit. The broadening of bands is ascribedo the change of effective acoustic impendence. The coupling effects onhe wave vector and negative dynamic modulus are discussed. Numericalimulations by finite element method further confirm the theoreticalesults. © 2008 American Institute of Physics.DOI: 10.1063/1.2839401

Three kinds of the periodical structures are designed as low-pass, high-pass, and band-pass filters for elastic wave. The theoretical simulations have proved that the periodical surface slots can act as a ow-pass filter for elastic wave. With increasing depth of the surface periodical structure in the sample,he cutoff frequency of the low-pass filter is decreased. Unlike the surface periodical structure, the eriodical subsurface structure can work as a high-pass filter for elastic wave. The cutoff frequency of the igh-pass filter is suppressed by the increase of the subsurface structure thickness. When the two eriodical structures are combined together, the band-pass filter is obtained, in which the pass band is etermined by the cutoff frequencies of the low-pass and high-pass filters. © 2009 American Institute of Physics. (DOI: 10.1063/1.3131043)

An acoustic cloak with concentric alternating layered structure is designed with homogeneous isotropic materials on the basis of effective medium theory. The cloak possesses low-reflection and power-flow bending properties for different shapes of wavefront both in far-and near-fields, which could perfectly approximate the ideal cloak with inhomogeneous and anisotropic distribution of material parameters. © 2008 American Institute of Physics.