A class of three-dimensional acoustic cloak for underwater operation is designed by using a multi-area coordinate transformation method. To overcome the difficulty of achieving materials with the ideal parameters of the cloak in nature, layered metamaterials consisting of mercury and water are designed based on effective medium theory. The acoustic properties of the layered metamaterials can be characterized by the anisotropic densities and isotropic modulus, which can satisfy the material requirements of the cloak shell. This design has many advantages over previous designs of acoustic cloak, including a large cloaking area, omnidirectional invisibility, broad working frequency and easier design methodology. Our transformation strategy and method of metamaterials design offer a cost-effective way and efficient technique for fabricating a large-scale cloak. Excellent invisibility is achieved by using simulations based on the finite element method. The good cloaking performances have demonstrated great potential in the promotion of the practical applications of a large-scale acoustic cloak, especially for lowfrequency sound manipulation underwater.
Narrow bandwidth and specific incident angle are the main drawbacks in real-life applications for the existed carpet cloaking based on the acoustic metasurface (AM). Here, we tackle to get over the problems by proposing a reprogrammable AM. The unit cell is composed of water sink and filling nozzle. By incorporating an external water pumping system into each individual unit cell, the reflected phase can be readily regulated. Since the pumping process is reversible, the AM is reprogrammable under the control of the water pumping system in the frequency range of 3430–6860[Formula: see text]Hz. Both the acoustic cloaking and disguising are designed based on the proposed AM. The double security for the target object can be ensured to avoid being detected by combining the two designs. Simulated results with the finite element method indicate that the acoustic cloaking and disguising can work in the broad bandwidth of 66.7% of the central frequency with full-range incident angles from [Formula: see text] to [Formula: see text]. Our design shows promise for applications in realizing the practical skin cloaking and disguising one step closer.
Asymmetric acoustic transmission (AAT) has been demonstrated using diverse acoustic metasurfaces (AMs). Here, we show that an emerging class of lossy AMs enables frequency-selective AAT. The asymmetric and symmetric transmissions can be realized at interested operating frequencies in specific incident angle ranges. The underlying mechanism is attributed to the inherent loss inside the labyrinthine structure of different arrangements. Our design introduces the freedom degree of frequency control for the achievement of the AAT devices.
Here, the frequency band-switchable topologically protected edge state transport is realized in simulation and experiment based on a 2 bit coding acoustic topological insulator that consists of two layers of sonic crystals arrayed by the Helmholtz resonant triangle-lattice scatters with two distinct rotation angles. The acoustic topological phase transition is revealed and the gapless frequency bands are predicted. Experimentally measured transmission spectra and simulated pressure fields show good agreement with the predicted results. The error between the measured and the predicted results is illustrated by introducing a slit into the nested scatters, which is comparable to the manufacturing accuracy of the commercial 3D printer. Our work provides a simple method of coding to achieve the frequency-switchable acoustic topological edge modes, and paves a promising way to design the intelligent, programmable, and flexible acoustic devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.