Special Issue "Acoustic Metamaterials"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Acoustics and Vibrations".

Deadline for manuscript submissions: 30 September 2018

Special Issue Editors

Guest Editor
Dr. Georgios Theocharis

CNRS Laboratoire d'Acoustique de l'Université du Maine, UMR-CNRS 6613, 72085 Le Mans Cedex 9, France
Website | E-Mail
Interests: acoustic metamaterials; phononic crystals; solitons; nonlinear dynamics
Co-Guest Editor
Dr. Vicent Romero-Garcia

CNRS Laboratoire d'Acoustique de l'Université du Maine, UMR-CNRS 6613, 72085 Le Mans Cedex 9, France
Website | E-Mail
Interests: acoustic metamaterials; acoustic metasurfaces; perfect absorption; phononic crystals
Co-Guest Editor
Prof. Dr. Olivier Richoux

Le Mans Université, Laboratoire d'Acoustique de l'Université du Maine, UMR-CNRS 6613, 72085 Le Mans Cedex 9, France
Website | E-Mail
Interests: acoustics; waves; lattice

Special Issue Information

Dear Colleagues,

Acoustic metamaterials are artificially-structured materials that can manipulate and control sound waves in ways that are not possible in conventional materials. It is an exciting and rapidly-expanding topic in the field of physical acoustics that, for more than 15 years now, has continued to give rise to exotic wave phenomena, such as acoustic cloaking, non-reciprocal propagation, parity–time-symmetric sound manipulation or waveguides immune to backscattering.  At the same time, new concepts, emerged by the intense research in the field of acoustic metamaterials, made acousticians and engineers to re-attack long-standing problems in acoustics, such as low frequency super absorption and to rethink the manufacturing of acoustic materials/devices with performance that surpasses the currently existing technology. 

This Special Issue will reveal both fundamental wave aspects of acoustic metamaterials as well as their practical perspectives. It provides a unique forum for discussion and presentation of recent advances. Scientists working in this broad field are invited to present their work in this Special Issue.

Dr. Georgios Theocharis
Dr. Vicente Romero García
Prof. Olivier Richoux
Guest Editor

Manuscript Submission Information

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Keywords

  • Acoustic metasurfaces

  • Locally resonant acoustic materials

  • Perfect absorption

  • PT symmetric metamaterials

  • Non-reciprocal propagation

  • Nonlinear metamaterials

  • Active metamaterials

  • Topological acoustics

Published Papers (7 papers)

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Research

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Open AccessArticle Broadening Bandgap Width of Piezoelectric Metamaterial by Introducing Cavity
Appl. Sci. 2018, 8(9), 1606; https://doi.org/10.3390/app8091606
Received: 3 August 2018 / Revised: 27 August 2018 / Accepted: 4 September 2018 / Published: 10 September 2018
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Abstract
In this research, a semi-analytical model of the adaptive piezoelectric metamaterial, built upon continuum mechanics characterization, was formulated and analyzed to reveal the fundamental features of bandgap with respect to unit-cell parameters under transverse wave. A new mechanism to broaden the bandgap width,
[...] Read more.
In this research, a semi-analytical model of the adaptive piezoelectric metamaterial, built upon continuum mechanics characterization, was formulated and analyzed to reveal the fundamental features of bandgap with respect to unit-cell parameters under transverse wave. A new mechanism to broaden the bandgap width, was then introduced through geometric cavity synthesis. It was demonstrated that the cavities incorporated into the host structure of the piezoelectric metamaterial can increase the electro-mechanical coupling of the system, which effectively yields broadened bandgap width. Case studies were performed to demonstrate the enhanced performance of the new design, as well as the tunability. Compared with the conventional piezoelectric metamaterial, the metamaterial with cavity synthesis can increase the bandgap width from 45 Hz to 126.7 Hz. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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Open AccessFeature PaperArticle Dark Solitons in Acoustic Transmission Line Metamaterials
Appl. Sci. 2018, 8(7), 1186; https://doi.org/10.3390/app8071186
Received: 10 June 2018 / Revised: 12 July 2018 / Accepted: 15 July 2018 / Published: 20 July 2018
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Abstract
We study dark solitons, namely density dips with a phase jump across the density minimum, in a one-dimensional, weakly lossy nonlinear acoustic metamaterial, composed of a waveguide featuring a periodic array of side holes. Relying on the electroacoustic analogy and the transmission line
[...] Read more.
We study dark solitons, namely density dips with a phase jump across the density minimum, in a one-dimensional, weakly lossy nonlinear acoustic metamaterial, composed of a waveguide featuring a periodic array of side holes. Relying on the electroacoustic analogy and the transmission line approach, we derive a lattice model which, in the continuum approximation, leads to a nonlinear, dispersive and dissipative wave equation. The latter, using the method of multiple scales, is reduced to a defocusing nonlinear Schrödinger equation, which leads to dark soliton solutions. The dissipative dynamics of these structures is studied via soliton perturbation theory. We investigate the role—and interplay between—nonlinearity, dispersion and dissipation on the soliton formation and dynamics. Our analytical predictions are corroborated by direct numerical simulations. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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Open AccessArticle Doppler-Based Acoustic Gyrator
Appl. Sci. 2018, 8(7), 1083; https://doi.org/10.3390/app8071083
Received: 30 May 2018 / Revised: 27 June 2018 / Accepted: 2 July 2018 / Published: 3 July 2018
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Abstract
Non-reciprocal phase shifters have been attracting a great deal of attention due to their important applications in filtering, isolation, modulation, and mode locking. Here, we demonstrate a non-reciprocal acoustic phase shifter using a simple acoustic waveguide. We show, both analytically and numerically, that
[...] Read more.
Non-reciprocal phase shifters have been attracting a great deal of attention due to their important applications in filtering, isolation, modulation, and mode locking. Here, we demonstrate a non-reciprocal acoustic phase shifter using a simple acoustic waveguide. We show, both analytically and numerically, that when the fluid within the waveguide is biased by a time-independent velocity, the sound waves travelling in forward and backward directions experience different amounts of phase shifts. We further show that the differential phase shift between the forward and backward waves can be conveniently adjusted by changing the imparted bias velocity. Setting the corresponding differential phase shift to 180 degrees, we then realize an acoustic gyrator, which is of paramount importance not only for the network realization of two port components, but also as the building block for the construction of different non-reciprocal devices like isolators and circulators. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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Open AccessArticle Structure and Sound Absorption Properties of Spiral Vane Electrospun PVA/PEO Nanofiber Membranes
Appl. Sci. 2018, 8(2), 296; https://doi.org/10.3390/app8020296
Received: 2 January 2018 / Revised: 5 February 2018 / Accepted: 12 February 2018 / Published: 17 February 2018
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Abstract
Noise pollution has become one of the four major pollution issues in the world and has drawn much attention recently. Controlling the sound source and using sound-absorbing materials reasonably is considered an effective way to reduce noise. Due to the high porosity and
[...] Read more.
Noise pollution has become one of the four major pollution issues in the world and has drawn much attention recently. Controlling the sound source and using sound-absorbing materials reasonably is considered an effective way to reduce noise. Due to the high porosity and specific surface area, nanofibers membrane is widely used in the field of the sound absorption. Polyvinyl alcohol (PVA) and Polyethylene oxide (PEO) are both water-soluble polymers with good film-forming properties that can be mixed in any proportion. In this paper, nanofiber membranes were prepared by spiral vane electrospinning with different contents of PVA and PEO. The nanofibers membranes were characterized by Fourier Transform-Infrared (FT-IR), X-ray diffraction (XRD), 3D-M, and scanning electron microscopy (SEM). The sound absorption property of nanofibers membranes and the compositions (nanofiber membranes and needle punched non-woven fabric) were tested with an impedance tube. The results demonstrate that the addition of PEO changed the morphological characteristics and construct of PVA, sound absorption properties had undergone great changes. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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Review

Jump to: Research

Open AccessReview A Review of Tunable Acoustic Metamaterials
Appl. Sci. 2018, 8(9), 1480; https://doi.org/10.3390/app8091480
Received: 5 July 2018 / Revised: 12 August 2018 / Accepted: 19 August 2018 / Published: 28 August 2018
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Abstract
Acoustic metamaterial science is an emerging field at the frontier of modern acoustics. It provides a prominent platform for acoustic wave control in subwavelength-sized metadevices or metasystems. However, most of the metamaterials can only work in a narrow frequency band once fabricated, which
[...] Read more.
Acoustic metamaterial science is an emerging field at the frontier of modern acoustics. It provides a prominent platform for acoustic wave control in subwavelength-sized metadevices or metasystems. However, most of the metamaterials can only work in a narrow frequency band once fabricated, which limits the practical application of acoustic metamaterials. This paper highlights some recent progress in tunable acoustic metamaterials based on various modulation techniques. Acoustic metamaterials have been designed to control the attenuation of acoustic waves, invisibility cloaking, and acoustic wavefront engineering, such as focusing via manipulating the acoustic impedance of metamaterials. The reviewed techniques are promising in extending the novel acoustics response into wider frequency bands, in that tunable acoustic metamaterials may be exploited for unusual applications compared to conventional acoustic devices. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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Open AccessReview An Integration Strategy for Acoustic Metamaterials to Achieve Absorption by Design
Appl. Sci. 2018, 8(8), 1247; https://doi.org/10.3390/app8081247
Received: 12 June 2018 / Revised: 2 July 2018 / Accepted: 23 July 2018 / Published: 27 July 2018
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Abstract
As much of metamaterials’ properties originate from resonances, the novel characteristics displayed by acoustic metamaterials are a narrow bandwidth and high dispersive in nature. However, for practical applications, broadband is often a necessity. Furthermore, it would even be better if acoustic metamaterials can
[...] Read more.
As much of metamaterials’ properties originate from resonances, the novel characteristics displayed by acoustic metamaterials are a narrow bandwidth and high dispersive in nature. However, for practical applications, broadband is often a necessity. Furthermore, it would even be better if acoustic metamaterials can display tunable bandwidth characteristics, e.g., with an absorption spectrum that is tailored to fit the noise spectrum. In this article we present a designed integration strategy for acoustic metamaterials that not only overcomes the narrow-band Achilles’ heel for acoustic absorption but also achieves such effect with the minimum sample thickness as dictated by the law of nature. The three elements of the design strategy comprise: (a) the causality constraint, (b) the determination of resonant mode density in accordance with the input target impedance, and (c) the accounting of absorption by evanescent waves. Here, the causality constraint relates the absorption spectrum to a minimum sample thickness, derived from the causal nature of the acoustic response. We have successfully implemented the design strategy by realizing three structures of which one acoustic metamaterial structure, comprising 16 Fabry-Perot resonators, is shown to exhibit near-perfect flat absorption spectrum starting at 400 Hz. The sample has a thickness of 10.86 cm, whereas the minimum thickness as dictated by the causality constraint is 10.55 cm in this particular case. A second structure demonstrates the flexible tunability of the design strategy by opening a reflection notch in the absorption spectrum, extending from 600 to 1000 Hz, with a sample thickness that is only 3 mm above the causality minimum. We compare the designed absorption structure with conventional absorption materials/structures, such as the acoustic sponge and micro-perforated plate, with equal thicknesses as the metamaterial structure. In both cases the designed metamaterial structure displays superior absorption performance in the target frequency range. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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Open AccessReview Acoustic Metamaterials in Aeronautics
Appl. Sci. 2018, 8(6), 971; https://doi.org/10.3390/app8060971
Received: 4 May 2018 / Revised: 4 June 2018 / Accepted: 7 June 2018 / Published: 13 June 2018
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Abstract
Metamaterials, man-made composites that are scaled smaller than the wavelength, have demonstrated a huge potential for application in acoustics, allowing the production of sub-wavelength acoustic absorbers, acoustic invisibility, perfect acoustic mirrors and acoustic lenses for hyper focusing, and acoustic illusions and enabling new
[...] Read more.
Metamaterials, man-made composites that are scaled smaller than the wavelength, have demonstrated a huge potential for application in acoustics, allowing the production of sub-wavelength acoustic absorbers, acoustic invisibility, perfect acoustic mirrors and acoustic lenses for hyper focusing, and acoustic illusions and enabling new degrees of freedom in the control of the acoustic field. The zero, or even negative, refractive sound index of metamaterials offers possibilities for the control of acoustic patterns and sound at sub-wavelength scales. Despite the tremendous growth in research on acoustic metamaterials during the last decade, the potential of metamaterial-based technologies in aeronautics has still not been fully explored, and its utilization is still in its infancy. Thus, the principal concepts mentioned above could very well provide a means to develop devices that allow the mitigation of the impact of civil aviation noise on the community. This paper gives a review of the most relevant works on acoustic metamaterials, analyzing them for their potential applicability in aeronautics, and, in this process, identifying possible implementation areas and interesting metabehaviors. It also identifies some technical challenges and possible future directions for research with the goal of unveiling the potential of metamaterials technology in aeronautics. Full article
(This article belongs to the Special Issue Acoustic Metamaterials)
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