Abstract: An acoustic device includes a three-dimensional phononic crystal having cubic symmetry. The phononic crystal includes a first region filled with a first material and a second region filled with a solid material that is different from the first material. The second region is the solid complement of the first region. A boundary between the first and second regions is shaped as a single gyroid surface that has constant mean curvature and is not pinched off. The volume of the second region is greater than or equal to that of the first region. The first material may be a gas, such as air, or a fluid. The phononic crystal supports topological surface states, has a band structure with at least one degenerate point protected by nonsymmorphic symmetry, and exhibits negative refraction where two of its external surfaces meet.

Abstract: An exemplary embodiment of the present invention provides a method of achieving a desired attenuation pattern in a material when a force is applied incident at least a portion of the material. The method comprises providing a multiphase material in a decompressed state, the multiphase material comprising a matrix material, a first periodic lattice of first inclusions positioned with the matrix material, and a second periodic lattice of second inclusions positioned within the matrix. The first periodic lattice of first inclusions can have a first set of lattice characteristics, and the second periodic lattice of second inclusions can have a second set of lattice characteristics different than the first set of lattice characteristics. The method can further comprise selecting the first and second sets of lattice characteristics based on a desired stress wave attenuation pattern when a force is applied incident to at least a portion of the multiphase material.

Abstract: Frequency-steerable acoustic transducers (FSATs) that allow directional generation or sensing of waves propagating in two-dimensional domains. Directionality is the result of the spatial filtering effect produced by the characteristic shape of the sensing surface. A wavenumber spiral FSAT (WS-FSAT) maps the direction of wave sensing in the [0°, 180°] range to a specific frequency component in the spectrum of the received signal. The use of a wavenumber spiral FSAT operating in sensing mode can be used for the localization of broadband acoustic events. One configuration includes a broadband source generating guided elastic waves in an isotropic plate. The WS-FSAT records the plate response and defines the source location through a time-frequency analysis of the received signal. The frequency selective response of the WS-FSAT directly maps the dominant component of the received signal to the direction of arrival of the incoming wave, thus greatly facilitating the source localization procedure.

Abstract: Systems and related methods for structural health monitoring are provided. In this regard, a representative array system includes: a component to be monitored; and an array system mounted to the component, the array system has multiple array components exhibiting spatial periodicity, the array components being operative to produce waves with frequency dependent directional characteristics, which propagate through the component, responsive to simultaneous activation of the array components.

Abstract: Systems and related methods for structural health monitoring are provided. In this regard, a representative array system includes: a component to be monitored; and an array system mounted to the component, the array system has multiple array components exhibiting spatial periodicity, the array components being operative to produce waves with frequency dependent directional characteristics, which propagate through the component, responsive to simultaneous activation of the array components.