Acoustic Magnifying Lens Based on Compact Non-Dispersive Spiral Metamaterial Array

2021 ◽  
Author(s):  
Li Xiang ◽  
Li Jian ◽  
Huang Xinjing
Keyword(s):  
Periodic Structures ◽  
Pressure Amplitude ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Alternate Route ◽  
Nondestructive Detection ◽  
Natural Materials ◽  
Compact Size ◽  
New Strategy ◽  
Focus Point

Abstract Acoustic magnifying lenses are utilized in a diversity of applications, from nondestructive detection of damages in materials to biomedical imaging. Acoustic metamaterials (MMs) provide powerful control over sound waves by using periodic structures made from natural materials. Existing acoustic meta-lens are commonly associated with designing dispersive metamaterial or connect with local resonator, thus resulting in inevitable deformity of waveforms. Although the four-blade spiral MMs has non-dispersive properties, how to further improve the transmission and reduce the manufacturing difficulty in a compact size is important to construction of a meta-lens. We propose a single-blade spiral metamaterial, which has higher transmission and non-dispersion properties. Based on this meta-unit, we designed and manufactured a meta-lens with the ability to amplify sound signals at the focus point. Different from previous research, the meta-lens is established by periodic meta-helicoid unit and presents great focusing ability while maintaining a compact volume. We show, both theoretically and experimentally, the thin flat acoustic magnifier can turn normally incident signals focusing on the prescribed point and augmenting pressure amplitude about three times. Moreover, the diameter of each element is only 10 mm, and the thickness of the meta-lens is 48mm. Our new strategy may offer an alternate route to the design of novel meta-lens and devices for acoustic application in the future.

scholarly journals Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1456 ◽  
Author(s):  
Reza Hedayati ◽  
Sandhya Lakshmanan
Keyword(s):  
Frequency Band ◽  
Open Space ◽  
Periodic Structures ◽  
Control Unit ◽  
Pressure Control ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Cavity Depth ◽  
Pneumatic Actuation ◽  
Actuation System

Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed- and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150–350 Hz to a frequency band of 300–600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies.

scholarly journals Bilayer ventilated labyrinthine metasurfaces with high sound absorption and tunable bandwidth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiayuan Du ◽  
Yuezhou Luo ◽  
Xinyu Zhao ◽  
Xiaodong Sun ◽  
Yanan Song ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Air Flow ◽  
Single Layer ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Sound Barrier ◽  
Free Air ◽  
Relative Bandwidth ◽  
Wide Range ◽  
High Sound

AbstractThe recent advent of acoustic metamaterials offers unprecedented opportunities for sound controlling in various occasions, whereas it remains a challenge to attain broadband high sound absorption and free air flow simultaneously. Here, we demonstrated, both theoretically and experimentally, that this problem can be overcome by using a bilayer ventilated labyrinthine metasurface. By altering the spacing between two constituent single-layer metasurfaces and adopting asymmetric losses in them, near-perfect (98.6%) absorption is achieved at resonant frequency for sound waves incident from the front. The relative bandwidth of absorption peak can be tuned in a wide range (from 12% to 80%) by adjusting the open area ratio of the structure. For sound waves from the back, the bilayer metasurface still serves as a sound barrier with low transmission. Our results present a strategy to realize high sound absorption and free air flow simultaneously, and could find applications in building acoustics and noise remediation.

Acoustic manipulation of fractal metamaterials with negative properties and near-zero densities

2021 ◽  
Author(s):  
Guanghua Wu ◽  
Yibo Ke ◽  
Lin Zhang ◽  
Meng Tao
Keyword(s):  
High Potential ◽  
Experimental Results ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Acoustic Device

Abstract Acoustic metamaterials have high potential in diverse applications, including acoustic cloaking, sound tunneling, wavefront reshaping, and sound insulation. In the present study, new metamaterials consisting of spatial coiled units are designed and fabricated to manipulate sound waves in the range 0-1600 Hz. The effective acoustic properties and band diagrams are studied. The simulation and experimental results demonstrate that the metamaterials provide an effective and feasible approach to design acoustic device such as sound cloaking and insulators.

scholarly journals Gradient index phononic crystals and metamaterials

Nanophotonics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 685-701 ◽  
Author(s):  
Yabin Jin ◽  
Bahram Djafari-Rouhani ◽  
Daniel Torrent
Keyword(s):  
Refractive Index ◽  
Wave Propagation ◽  
Acoustic Waves ◽  
Effective Properties ◽  
Periodic Structures ◽  
Phononic Crystals ◽  
Ray Theory ◽  
Acoustic Metamaterials ◽  
Propagation Of Waves ◽  
At Will

AbstractPhononic crystals and acoustic metamaterials are periodic structures whose effective properties can be tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible to locally change the properties of a finite crystal in such a way that it results in an effective gradient of the refractive index. In such case the propagation of waves can be accurately described by means of ray theory, and different refractive devices can be designed in the framework of wave propagation in inhomogeneous media. In this paper we review the different devices that have been studied for the control of both bulk and guided acoustic waves based on graded phononic crystals.

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.

Elastic Wave Propagation in a Bio-Inspired Phononic Crystal

2020 ◽  
Vol 1012 ◽  
pp. 9-13
Author(s):  
H.V. Cantanhêde ◽  
E.J.P. Miranda Jr. ◽  
J.M.C. dos Santos
Keyword(s):  
Wave Propagation ◽  
Band Structure ◽  
Vibrational Energy ◽  
Periodic Structures ◽  
Chemical Elements ◽  
Phononic Crystal ◽  
Stop Band ◽  
Elastic Vibration ◽  
Band Gaps ◽  
Sound Waves

The wave propagation in a two-dimensional bio-inspired phononic crystal (PC) is analysed. When composite materials and structures consist of two or more different materials periodically, there will be stop band characteristic, in which there are no mechanical propagating waves. These periodic structures are known as PCs. PCs have shown an excellent potential in many disciplines of science and technology in the last decade. They have generated lots of interests due to their ability to manipulate mechanical waves like sound waves and thermal properties which are not available in nature. The physical properties of PCs are not essentially determined by chemical elements and bonds in the materials, but rather on the internal specific structures. Structures of this type have the ability to inhibit the propagation of vibrational energy over certain ranges of frequencies forming band gaps. The main purpose of this study is to investigate the band structure and especially the location and width of band gaps. For this analysis, it is used the finite element method (FEM) and plane wave expansion (PWE). The results are shown in the form of band structure and wave modes. Band structures calculated by FEM and PWE present good agreement. We suggest that the bio-inspired PC considered should be feasible for elastic vibration control.

scholarly journals The Effect of Geometrical Parameters on Resonance Characteristics of Acoustic Metamaterials with Negative Effective Modulus

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Xiao-Le Yan ◽  
Li-Mei Hao ◽  
Mei-Ling Men ◽  
Zhi Chen
Keyword(s):  
Resonance Frequency ◽  
Analytical Formula ◽  
Blue Shift ◽  
Theory Model ◽  
Outer Radius ◽  
Effective Modulus ◽  
Geometrical Parameters ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Acoustic Metamaterial

There has been an explosion of interest in acoustic metamaterial in the last ten years. The tunable negative acoustic metamaterial is an important issue for designing metamaterials. The acoustic metamaterial is restricted by the narrow bandgap of sound waves for the local resonance of metamaterial unit cells. By shifting the sizes of the unit cell, the acoustic metamaterial could potentially overcome the limit of the narrow resonance frequency. In this research, we focus on the resonant behavior of split hollow sphere (SHS) in the waveguide. Firstly, we analyze the resonance characteristics of SHS and get an analytical formula for the effect of geometrical parameters on the resonance frequency. Furthermore, the resonance frequency of SHS is verified with finite-element method analysis based on COMSOL Multiphysics simulation. The results are in good agreement with theory model. It is observed that there is a blue shift of the resonance frequency with the gradual increase of the neck radius of SHS, a V-type response curve with the increase of inner radius of SHS, and a red shift with the increase of outer radius of SHS. Using the method of estimate of resonance, we could get a precisely controllable unit structure with negative effective modulus and offer a way to optimize the realization of double negative acoustic metamaterial.

scholarly journals On the acoustic radiation pressure on spheres

1934 ◽  
Vol 147 (861) ◽  
pp. 212-240 ◽  
Keyword(s):  
Radiation Pressure ◽  
Acoustic Radiation ◽  
Wave Length ◽  
Theoretical Development ◽  
Order Effects ◽  
Pressure Amplitude ◽  
Sound Waves ◽  
Radiation Fields ◽  
Acoustic Radiation Pressure ◽  
Relative Measurements

Although frequent reference is made to acoustic radiation pressure in treatises and memoirs on sound, there appears to be no systematic theoretical development of the subject enabling actual pressures on obstacles of simple geometrical form to be calculated. In the audible range of acoustic frequencies, it is possible to devise, in a number of ways, means of measuring pressure amplitudes in sound waves as first order effects. At supersonic frequencies, however, these methods are no longer serviceable. When the dimensions of resonators of diaphragms become comparable with the wave-length, the physical effects which enable the pressure amplitude to be measured involve intractable diffraction problems, while the extremely high frequencies and small amplitudes involved make the employment of stroboscopic methods of observation extremely difficult. It has been shown, however, that at supersonic frequencies the acoustic radiation pressures on spheres and discs become sufficiently large to be measured easily, at any rate, in liquids. The mean pressure is generally assumed to be proportional to the energy density in the neighbourhood of the obstacle, and on this basis relative measurements can be made, for instance, in the radiation field of a supersonic oscillator. Such formulæ may be obtained without restriction as to wave-length, for spheres in plane progressive and stationary radiation fields, and the magnitude of the pressure is found to be of entirely different orders of magnitude in the two cases.

scholarly journals Breaking the barriers: advances in acoustic functional materials

2017 ◽  
Vol 5 (2) ◽  
pp. 159-182 ◽  
Author(s):  
Hao Ge ◽  
Min Yang ◽  
Chu Ma ◽  
Ming-Hui Lu ◽  
Yan-Feng Chen ◽  
...  
Keyword(s):  
Negative Refraction ◽  
Functional Materials ◽  
Building Blocks ◽  
The Novel ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Symmetry Principle ◽  
Active Metamaterials ◽  
Wavelength Scale ◽  
Phase Engineering

Abstract Acoustics is a classical field of study that has witnessed tremendous developments over the past 25 years. Driven by the novel acoustic effects underpinned by phononic crystals with periodic modulation of elastic building blocks in wavelength scale and acoustic metamaterials with localized resonant units in subwavelength scale, researchers in diverse disciplines of physics, mathematics, and engineering have pushed the boundary of possibilities beyond those long held as unbreakable limits. More recently, structure designs guided by the physics of graphene and topological electronic states of matter have further broadened the whole field of acoustic metamaterials by phenomena that reproduce the quantum effects classically. Use of active energy-gain components, directed by the parity–time reversal symmetry principle, has led to some previously unexpected wave characteristics. It is the intention of this review to trace historically these exciting developments, substantiated by brief accounts of the salient milestones. The latter can include, but are not limited to, zero/negative refraction, subwavelength imaging, sound cloaking, total sound absorption, metasurface and phase engineering, Dirac physics and topology-inspired acoustic engineering, non-Hermitian parity–time synthetic active metamaterials, and one-way propagation of sound waves. These developments may underpin the next generation of acoustic materials and devices, and offer new methods for sound manipulation, leading to exciting applications in noise reduction, imaging, sensing and navigation, as well as communications.

scholarly journals Bilayer ventilated labyrinthine metasurfaces with high sound absorption and tunable bandwidth

2020 ◽  
Author(s):  
Jiayuan Du ◽  
Yuezhou Luo ◽  
Xinyu Zhao ◽  
Xiaodong Sun ◽  
Yanan Song ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Air Flow ◽  
Single Layer ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Sound Barrier ◽  
Free Air ◽  
Relative Bandwidth ◽  
Wide Range ◽  
High Sound

Abstract The recent advent of acoustic metamaterials offers unprecedented opportunities for sound controlling in various occasions, whereas it remains a challenge to attain broadband high sound absorption and free air flow simultaneously. Here, we demonstrated, both theoretically and experimentally, that this problem can be overcome by using a bilayer ventilated labyrinthine metasurface. By altering the spacing between two constituent single-layer metasurfaces and adopting asymmetric losses in them, near-perfect (98.6%) absorption is achieved at resonant frequency for sound waves incident from the front. The relative bandwidth of absorption peak can be tuned in a wide range (from 12% to 80%) by adjusting the open area ratio of the structure. For sound waves from the back, the bilayer metasurface still serves as a sound barrier with low transmission. Our results present a strategy to realize high sound absorption and free air flow simultaneously, and could find applications in building acoustics and noise remediation.

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