scholarly journals An Integration Strategy for Acoustic Metamaterials to Achieve Absorption by Design

2018 ◽  
Vol 8 (8) ◽  
pp. 1247 ◽  
Author(s):  
Min Yang ◽  
Ping Sheng
Keyword(s):  
Absorption Spectrum ◽  
Perforated Plate ◽  
Design Strategy ◽  
Sample Thickness ◽  
Acoustic Metamaterials ◽  
Metamaterial Structure ◽  
Minimum Thickness ◽  
Practical Applications ◽  
Integration Strategy ◽  
Minimum Sample

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.

scholarly journals Tunable Fluid-Type Metasurface for Wide-Angle and Multifrequency Water-Air Acoustic Transmission

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhandong Huang ◽  
Shengdong Zhao ◽  
Yiyuan Zhang ◽  
Zheren Cai ◽  
Zheng Li ◽  
...  
Keyword(s):  
Incident Angle ◽  
Acoustic Energy ◽  
Wide Angle ◽  
Acoustic Metamaterials ◽  
Fluid Type ◽  
Acoustic Transmission ◽  
Interface Instability ◽  
Practical Applications ◽  
Air Interface ◽  
Transmission Enhancement

Efficient acoustic communication across the water-air interface remains a great challenge owing to the extreme acoustic impedance mismatch. Few present acoustic metamaterials can be constructed on the free air-water interface for enhancing the acoustic transmission because of the interface instability. Previous strategies overcoming this difficulty were limited in practical usage, as well as the wide-angle and multifrequency acoustic transmission. Here, we report a simple and practical way to obtain the wide-angle and multifrequency water-air acoustic transmission with a tunable fluid-type acoustic metasurface (FAM). The FAM has a transmission enhancement of acoustic energy over 200 times, with a thickness less than the wavelength in water by three orders of magnitude. The FAM can work at an almost arbitrary water-to-air incident angle, and the operating frequencies can be flexibly adjusted. Multifrequency transmissions can be obtained with multilayer FAMs. In experiments, the FAM is demonstrated to be stable enough for practical applications and has the transmission enhancement of over 20 dB for wide frequencies. The transmission enhancement of music signal across the water-air interface was performed to demonstrate the applications in acoustic communications. The FAM will benefit various applications in hydroacoustics and oceanography.

scholarly journals Wavefront manipulation by acoustic metasurfaces: from physics and applications

Nanophotonics ◽  
2018 ◽  
Vol 7 (6) ◽  
pp. 1191-1205 ◽  
Author(s):  
Bin Liang ◽  
Jian-chun Cheng ◽  
Cheng-Wei Qiu
Keyword(s):  
Acoustic Waves ◽  
Review Paper ◽  
Three Dimensional ◽  
New Physics ◽  
Research Field ◽  
Acoustic Metamaterials ◽  
Future Directions ◽  
Practical Applications ◽  
The Past ◽  
Recent Developments

AbstractMolding the wavefront of acoustic waves into the desired shape is of paramount significance in acoustics, which however are usually constrained by the acoustical response of naturally available materials. The emergence of acoustic metamaterials built by assembling artificial subwavelength elements provides distinct response to acoustic waves unattainable in nature. More recently, acoustic metasurfaces, a class of metamaterials with a reduced dimensionality, empower new physics and lead to extended functionalities different from their three-dimensional counterparts, enabling controlling, transmitted or reflected acoustic waves in ways that were not possible before. In this review paper, we present a comprehensive view of this rapidly growing research field by introducing the basic concepts of acoustic metasurfaces and the recent developments that have occurred over the past few years. We review the interesting properties of acoustic metasurfaces and their important functionalities of wavefront manipulation, followed by an outlook for promising future directions and potential practical applications.

Sub-Bandgap Optical Absorption in Amorphous Silicon using Photo-Pyroelectric Spectroscopy

1991 ◽  
Vol 219 ◽  
Author(s):  
J. Fan ◽  
J. Kakalios
Keyword(s):  
Absorption Spectrum ◽  
Optical Absorption ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Wavelength Dependence ◽  
Sample Thickness ◽  
Pyroelectric Effect ◽  
Radiative Quantum Efficiency ◽  
Set Up ◽  
Hydrogenated Amorphous

ABSTRACTMeasurements of the optical absorption spectrum of doped and undoped hydrogenated amorphous silicon (a-Si:H) for photon energies ranging from 0.8 to 2.5 eV are obtained using photo-pyroelectric spectroscopy (PPES). This technique, based upon the pyroelectric effect, has a simpler experimental set-up than photo-thermal deflection spectroscopy, and presently has a sensitivity of ad > 10-3, where d is the sample thickness. In addition, using PPES we have measured the non-radiative quantum efficiency in a-Si:H, and find that it has a strong wavelength dependence for sub-bandgap illumination.

scholarly journals MECHANICS AND ACOUSTICS OF METAMATERIALS: MATHEMATICAL MODELING, EXPERIMENTAL RESEARCH, PROSPECTS FOR APPLICATION IN MECHANICAL ENGINEERING

2021 ◽  
Vol 83 (4) ◽  
pp. 391-414
Author(s):  
V.I. Erofeev ◽  
I.S. Pavlov
Keyword(s):  
Electromagnetic Waves ◽  
Physical And Mechanical Properties ◽  
Structural Modeling ◽  
Analytical Relationship ◽  
Acoustic Metamaterials ◽  
Practical Applications ◽  
Advantages And Disadvantages ◽  
Mechanical Metamaterials ◽  
Microstructure Parameters ◽  
The Creation

An overview of modern publications on acoustic and mechanical metamaterials is presented. The most important characteristic feature of metamaterials is the presence of frequency band gaps in them, i.e. such frequencies at which the waves cannot propagate in the material. This feature has played a major role in the creation of acoustic metamaterials that are successfully used to absorb sound, to damp vibration and shock effects, and to make devices preventing the propagation of waves on a given frequency in certain directions. Such representatives of mechanical metamaterials as auxetics – materials, at least one of the Poisson's ratios of which is negative, have also proven themselves as advanced materials for practical applications. They are distinguished by high consumer value (low density, high strength, nice insulating properties). In addition to acoustics and mechanics, in recent years there has been a significant increase in interest in the creation of materials that make it possible to control the flow of light or electromagnetic waves. It has been also noted that the development of new metamaterials is in high demand for the aerospace and automotive industries, as well as for biomedical applications. Two basic methods for modeling of metamaterials are considered: the continual-phenomenological description and the structural modeling. Their advantages and disadvantages are listed. The structural modeling method enables one establishing an analytical relationship between the medium macroconstants and its microstructure parameters. As a result, there appears a possibility both to get an idea of the qualitative influence of the microstructure of the medium on its effective elastic moduli and to estimate quantitatively these constants, as well as to find the ranges of values of the microstructure parameters at which the medium possesses unique physical and mechanical properties.

The Role of Nonlinear Acoustic Boundary Conditions in Combustion/Acoustic Coupled Instabilities

2009 ◽  
Author(s):  
T. Schuller ◽  
N. Tran ◽  
N. Noiray ◽  
D. Durox ◽  
S. Ducruix ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Perforated Plate ◽  
Mode Switching ◽  
Describing Function ◽  
Complex Flow ◽  
Acoustic Boundary Conditions ◽  
Practical Applications ◽  
Bias Flow ◽  
Flow Interactions ◽  
Flame Response

Triggering, frequency shifting, mode switching and hysteresis are commonly encountered during self-sustained oscillations in combustors. These mechanisms cannot be anticipated from classical linear stability analysis and the nonlinear flame response to incident flow perturbations is often invoked to interpret these features. However, the flame may not be solely responsible for nonlinearities. Recent studies indicate that interactions with boundaries can be influenced by the perturbation level and that this needs to be considered. The nonlinear response of acoustic boundary conditions to flow perturbations is here exemplified in two configurations which typify practical applications. The first corresponds to a perforated plate backed by a cavity conveying a bias flow and the second corresponds to a set of flames stabilized at a burner outlet. These systems are submitted to acoustic perturbations of increasing amplitudes as can be encountered during unstable operation. It shown that these terminations can be characterized by an impedance featuring an amplitude dependent response. The classical linear impedance Z(ω) is then replaced by its nonlinear counterpart an Impedance Describing Function (IDF), which depends on the perturbation level input Z(ω, |p′| or |u′|). Using this concept, it is shown that the passive perforated plate optimized to damp instabilities of small amplitudes may eventually loose its properties when submitted to large sound pressure levels and that the flame response shifts when the amplitude of incoming flow perturbations is amplified. The influence of these nonlinear elements on the stability of a generic burner is then examined using a methodology which extends a previous analysis based on the Flame Describing Function (FDF) to systems with complex flow interactions at the boundaries.

scholarly journals Numerical Investigation of Discrepancies Between Two-Dimensional and Three-Dimensional Acoustic Metamaterials

2021 ◽  
Vol 8 ◽  
Author(s):  
Wenchao Jin ◽  
Hui Guo ◽  
Pei Sun ◽  
Yansong Wang ◽  
Tao Yuan
Keyword(s):  
Band Structure ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Experimental Models ◽  
Mode Shapes ◽  
Periodic Lattice ◽  
Two Dimensional ◽  
Acoustic Metamaterials ◽  
Band Structures ◽  
Practical Applications

In order to get insight information of the band structure of acoustic metamaterials (AMMs) in condensed matter, periodic lattice structures are analyzed using Bloch’s theorem. Typical approaches of the band structure computation methods, topology optimization, and tunable abilities cannot overcome the gap between the two-dimensional (2D) AMMs theoretical and three-dimensional (3D) specimens’ experimental data yet. In this work, the variation in the results of the band structure obtained from the 2D mathematical model computed with respect to the 3D experimental models, and related cause of the variation is explored. The band structures and mode shapes of the 2D AMMs, quasi-2D models, and 3D specimen models are followed to reveal the boundary conditions and source for the observed differences in band structures. The cause for the discrepancies is verified by using the finite element method (FEM) with corresponding boundary conditions. It is found that outcomes from computational data of the 2D AMMs model are diverted significantly by means of bandgap, band structure, and stress distribution in counterparts of the 3D specimen model. This approach can provide assistance for computing the band structure of 2D AMMs for practical applications.

Multi-mass synergetic coupling perforated bi-layer plate-type acoustic metamaterials for sound insulation

2020 ◽  
Vol 34 (13) ◽  
pp. 2050136
Author(s):  
Weikang Huang ◽  
Tianning Chen ◽  
Quanyuan Jiang ◽  
Xinpei Song ◽  
Wuzhou Yu ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Perforated Plate ◽  
Low Frequency ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Acoustic Metamaterials ◽  
Practical Engineering ◽  
Broadband Sound ◽  
Insulation Performance ◽  
Plate Type

Thin plate-type acoustic metamaterials have the advantages of lightweight, high rigidity and adjustable parameters, showing great practical application values in sound wave control. In this paper, a type of perforated bi-layer plate-type acoustic metamaterials (PBPAM) is designed for low-frequency noise control. The sound insulation peaks can be increased by combining the perforated plate and synergetic masses, making the sound insulation performance close to the mass law at the resonant frequency. Compared to the results predicted by the mass law, a better performance of sound insulation is achieved based on the PBPAM. The effects of the structural parameters are investigated in this study. Based on the impedance tube experiments, the measured results have a good agreement with the simulated ones. This work can provide a reference for low-frequency and broadband sound insulation based on plate-type acoustic metamaterials in practical engineering.

scholarly journals Bent-Shaped p-Type Small-Molecule Organic Semiconductors: A Molecular Design Strategy for Next-Generation Practical Applications

2020 ◽  
Vol 142 (20) ◽  
pp. 9083-9096 ◽  
Author(s):  
Toshihiro Okamoto ◽  
Craig P. Yu ◽  
Chikahiko Mitsui ◽  
Masakazu Yamagishi ◽  
Hiroyuki Ishii ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Small Molecule ◽  
Molecular Design ◽  
Design Strategy ◽  
Next Generation ◽  
Practical Applications ◽  
P Type

Viscoelastic multi-resonator mechanism for broadening low-frequency band-gap of acoustic metamaterials

2019 ◽  
Vol 86 (1) ◽  
pp. 10901 ◽  
Author(s):  
Hongxing Liu ◽  
Jiu Hui Wu
Keyword(s):  
Elastic Modulus ◽  
Band Gap ◽  
Frequency Band ◽  
Loss Modulus ◽  
Great Influence ◽  
Low Frequency ◽  
Band Gaps ◽  
Band Width ◽  
Acoustic Metamaterials ◽  
Practical Applications

In this paper, viscoelastic multi-resonator mechanism for broadening low-frequency band-gaps of acoustic metamaterials is investigated. Firstly, the metamaterial unit consists of dual-mass and dual-viscoelasticity is proposed which can generate multiple resonances to form multiple band-gaps, and further the broadened band-gaps are realized by modulating the effect of the viscoelasticity. Secondly, for the dual-viscoelasticity, the band-gaps and transmission spectrum under the cases of with the consistent and inconsistent viscoelasticity are calculated. Comparing with the consistent case, by adjusting the viscoelasticity in the inconsistent case, the storage modulus changes the fastest and obtains a smaller and a larger elastic modulus at the corresponding starting frequency and ending frequency of the band-gap, in which the band-gap can be broadened and shifted to the low frequency since the resonant frequency is determined by the elastic modulus, and for the loss modulus, it has little effects on the width of the band-gap, but has great influence on the transmission coefficient. Thirdly, by adjusting the inconsistent viscoelastic parameters based on the above rules, the band width is increased by 1.7 times (1.3 times for the absolute band width) than the consistent structure and the band-gap is shifted to the low frequency by 31% (about 345 Hz). The viscoelastic multi-resonator mechanism can be used to practical applications of viscoelastic metamaterials.

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