The use of acoustic resonators for characterization of underwater acoustic metamaterials

2017 ◽  
Vol 142 (4) ◽  
pp. 2684-2684
Author(s):  
Preston S. Wilson ◽  
Michael R. Haberman
Keyword(s):  
Acoustic Metamaterials ◽  
Underwater Acoustic ◽  
Acoustic Resonators

Tunable underwater acoustic metamaterials via quasi-Helmholtz resonance: From low-frequency to ultra-broadband

2021 ◽  
Vol 118 (7) ◽  
pp. 071904
Author(s):  
Mingyu Duan ◽  
Chenlei Yu ◽  
Fengxian Xin ◽  
Tian Jian Lu
Keyword(s):  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Underwater Acoustic ◽  
Helmholtz Resonance

scholarly journals Fabrication and Characterization of 3D Printed Thin Plates for Acoustic Metamaterials Applications

2019 ◽  
Vol 19 (22) ◽  
pp. 10365-10372
Author(s):  
Cecilia Casarini ◽  
Vicent Romero-Garcia ◽  
Jean-Philippe Groby ◽  
Benjamin Tiller ◽  
James F. C. Windmill ◽  
...  
Keyword(s):  
Thin Plates ◽  
Acoustic Metamaterials ◽  
3D Printed ◽  
Fabrication And Characterization

scholarly journals A Composite Perforated Partitioned Sandwich Panel With Corrugation for Underwater Low-Frequency Sound Absorption

2021 ◽  
Vol 7 ◽  
Author(s):  
Junyi Wang ◽  
Jiaming Hu ◽  
Yun Chen
Keyword(s):  
Acoustic Wave ◽  
Composite Structure ◽  
Sound Absorption ◽  
Low Frequency ◽  
Propagation Loss ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Underwater Sound ◽  
Underwater Acoustic ◽  
Frequency Sound

Underwater acoustic wave absorption and control play an important role in underwater applications. Various types of underwater acoustic metamaterials have been proposed in recent years with the vigorous development of acoustic metamaterials. Compared with airborne sound, underwater sound waves have a longer wavelength and much smaller propagation loss, making them more difficult to control. In addition, given that the acoustic impedance of water is much greater than that of air, numerous conventional materials and structures are not suited to underwater use. In this paper, we propose a composite structure based on an excellent broadband low-frequency sound absorber of air using aluminum mixed with rubber. Our composite structure possesses broadband low-frequency (<1,000 Hz) sound absorption underwater, omnidirectional high sound absorption coefficient under the oblique incidence (0–75°), and pressure resistance. It has promising applications for underwater acoustic wave control and contributes to the design of underwater acoustic metamaterials.

scholarly journals Observation of higher-order non-Hermitian skin effect

2021 ◽  
Author(s):  
Xiujuan Zhang ◽  
Yuan Tian ◽  
Jian-Hua Jiang ◽  
Ming-Hui Lu ◽  
Yan-Feng Chen
Keyword(s):  
Degrees Of Freedom ◽  
Skin Effect ◽  
Higher Order ◽  
Dependent Manner ◽  
Acoustic Metamaterials ◽  
Opposite Edge ◽  
Band Theory ◽  
Acoustic Resonators ◽  
Fermi Arcs ◽  
Spin Polarized

Abstract Hermitian theories play a major role in understanding the physics of most phenomena. It has been found only in the past decade that non-Hermiticity enables unprecedented effects such as exceptional points, spectral singularities and bulk Fermi arcs. Recent studies further show that non-Hermiticity can fundamentally change the topological band theory, leading to the non-Hermitian band topology and non-Hermitian skin effect, as confirmed in one-dimensional (1D) systems. However, in higher dimensions, these non-Hermitian effects remain unexplored in experiments. Here, we demonstrate the spin-polarized, higher-order non-Hermitian skin effect in two-dimensional (2D) acoustic metamaterials. Using a lattice of coupled whisper-gallery acoustic resonators, we realize a spinful 2D higher-order topological insulator (HOTI) where the spin-up and spin-down states are emulated by the anti-clockwise and clockwise modes, respectively. We find that the non-Hermiticity drives wave localizations toward opposite edge boundaries depending on the spin polarizations. More interestingly, for finite systems with both edge and corner boundaries, the higher-order non-Hermitian skin effect leads to wave localizations toward two corner boundaries for the bulk, edge and corner states in a spin-dependent manner. We further show that such a non-Hermitian skin effect enables rich wave manipulation through the loss configuration in each unit-cell. The reported spin-dependent, higher-order non-Hermitian skin effect reveals the interplay between higher-order topology and non-Hermiticity, which is further enriched by the spin degrees of freedom. This unveils a new horizon in the study of non-Hermitian physics and the design of non-Hermitian metamaterials.

scholarly journals Underwater Acoustic Channel Characterization of Shallow Water Environment

2018 ◽  
Vol 6 (1) ◽  
pp. 137-150 ◽  
Author(s):  
Tri Budi Santoso ◽  
Endang Widjiati ◽  
Wirawan Wirawan ◽  
Gamantyo Hendrantoro
Keyword(s):  
Shallow Water ◽  
Channel Model ◽  
Delay Spread ◽  
Underwater Acoustic Communication ◽  
Underwater Acoustic Channel ◽  
Underwater Acoustic ◽  
Acoustic Channel ◽  
Measurement Result ◽  
Maximum Delay

Understanding of channel propagation characteristics is a key to the optimal design of underwater acoustic communication. Generally, modelling of underwater acoustic channel is performed based on measurement result in certain site at certain times. Different sites might have different characteristics, each of which can generally be described by a model obtained by averaging measurement results at multiple points in the same environment. This paper describes a characterization of the underwater acoustic channel of tropical shallow water in a Mangrove estuary, which has sediment up to 60 cm at the bottom. Such a channel model is beneficial for the design of communication system in an autonomous underwater vehicle, for instance. The measurement result of delay spread parameter from three different points with the distance of 14 ~ 52 m, has various values. The root mean square (RMS) of delay spread ranges between 0.0621 ~ 0.264 ms, and the maximum delay spread varies with the value of 0.187 ~ 1.0 ms. The pdf fitting shows that Rayleigh distribution describes the fading variation more accurately than Nakagami and Ricean.

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