Acoustic wave redirection and sensing using bianisotropic acoustic metamaterials
Abstract
Acoustic metamaterials offer significant promise for the creation of heterogeneous passive acoustic materials to improve the performance of specific areas of high importance to the Navy. Of specific interest here are materials exhibiting acoustic bianisotropy, which have only very recently garnered attention of the scientific community. Materials possessing this property are of high interest because they provide the scientist with additional parameters to design the specific acoustic impedance of the material. Acoustic impedance is the ratio of the pressure and particle velocity associated with waves propagating in the medium. It is the characteristic plane-wave impedance that dictates how waves behave at the interface between two materials and it is therefore of paramount importance if one wishes to control acoustic fields using passive acoustic materials. Bianisotropy, which emerges because of subwavelength asymmetries and long-range order in the material, allows one to control the acoustic impedance, and therefore provides a means to tailorthe anisotropic complex impedance of an acoustic medium through the design of its subwavelength structure in ways that have yet to be fully investigated by the scientific community. Bianisotropic AMM are therefore strong candidates for engineered surfaces to redirect, focus, and diffuse underwater sound fields. While several works exist on the topic of dynamic homogenization and the emergence of bianisotropic behavior, there has been essentially no demonstration or exploration of the utility of this behavior for applications of interest to the Navy. The over-arching objective of the proposed research is thus to explore the design space offered by bianisotropic AMM through modeling, design, and experiment. The proposed research will investigate the utilityof these materials for the control of reflected and transmitted acoustic fields using sub-wavelength thickness surfaces. Further, the materials developed will be used to investigate improvements to underwater acoustic sensing systems by leveraging modeling and design tools developed by this work to design bianisotropic layers that enable one to tailor the phase of reflected or transmittedacoustic fields as a function of length along the layer. The spatially varying phase response can then be used to create acoustic lenses, matching layers, or windows to improve the performance of acoustic sensing devices. The proposed effort is organized around two complementary research thrusts. The first thrust will focus on modeling emergent bianisotropy resulting from subwavelength material and structural asymmetries as well as long-range order. This effort will include analytical, finite element method (FEM), and hybrid analytical-FEM approaches. The second thrust will make use of the modeling tools developed in the first thrust to design subwavelength structure that generates acoustic bianisotropy and to then fabricate material samplesfor experimental demonstration of the utility of bianisotropy to control acoustic fields for redirection of acoustic energy and to enhance acoustic sensing capabilities.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N000141812335
Entities
People
- Michael R Haberman
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Austin