scholarly journals Development of acoustic metamaterials for efficient sound control noise mitigation

2021 ◽  
Author(s):  
◽  
Huy Nguyen
Keyword(s):  
Fano Resonance ◽  
High Performance ◽  
Noise Control ◽  
Single Layer ◽  
Acoustic Metamaterials ◽  
Noise Mitigation ◽  
Short Channel ◽  
Low Frequencies ◽  
Helmholtz Resonators ◽  
Unit Cells

Acoustic metamaterials have been studied intensively recently since they can expose unnatural-born properties, potentially breaking the capacity limits of conventional acoustic materials. Since these interesting properties are mostly observed around metamaterials' local resonances/anti-resonance, resonance-based acoustic metamaterials are most popular in developing metamaterials. Employing resonance-based unnatural born properties such as effective negative mass density, effective negative bulk modulus, and acoustic hyper-damping on designing noise control solutions can give excellent devices showing such high performance that conventional acoustic material cannot achieve. This dissertation is an effort to employ acoustic metamaterials in designing efficient noise control. First, membrane-type acoustic metamaterials (MAM) will be employed to design a lightweight acoustic panel with high sound transmission loss (STL) in broadband at low frequencies. Negative density at around the anti-resonance of MAM gives it high capability on blocking sound. A double MAM-layer structure is proposed to double the STL performance of unit cells theoretically. Therein, simulation by using COMSOL Multiphysics is the main tool to optimize the unit cell design, panel structure, and effect of panel frame's vibration. Fabrication of the optimal design and experiments are also conducted to verify the calculation and simulation predictions. In addition to the acoustic panel, MAM is used to design a highly efficient acoustic energy harvester working at low frequencies. A magnet coin is deployed close to a magnet coil attached to the mass of MAM. The maximum oscillation of the coil due to MAM's first local resonance will induce a strong electric current inside the coil. Hence, energy can be harvested by an external resistor representing loads of harvesting devices. A complete theoretical model of the harvester is also developed in order to optimize its performance. Multiphysics simulation is conducted to verify the theoretical predictions. Besides MAM, Helmholtz has been used to design a high-performance and broadband acoustic silencer. Specifically, five slit-type Helmholtz resonators, which possess a massive viscous area, are packed together to create a single-layer silencer. In turn, two single-layer silencers are combined to form a double-layer silencer, which in theory double performance on noise blocking of the single-layer silencer. Theoretical models of slit-type Helmholtz resonators and silencers are developed completely and well validated with simulation and experimental results. Finally, Fano resonance resulting from the coupling between resonant and non-resonant channels will be explored and employed to design an ultra-broadband acoustic barrier with high ventilation. The resonant channel is generally represented a space-coiling channel, and the non-resonant channel represents ventilation or a straight and short channel. First, the formation of coupling Fano resonance will be theoretically addressed. Subsequently, acoustic hyper-damping is proposed by integrating thin acoustic foams into velocity anti-nodes in the resonant channel. In the end, an ultra-broadband acoustic barrier with high ventilation and STL is designed by employing three rows of hyper-dampened unit cells. Fabrication and experiment also are conducted to verify the simulation prediction.

scholarly journals Moth wings are acoustic metamaterials

2020 ◽  
Vol 117 (49) ◽  
pp. 31134-31141 ◽  
Author(s):  
Thomas R. Neil ◽  
Zhiyuan Shen ◽  
Daniel Robert ◽  
Bruce W. Drinkwater ◽  
Marc W. Holderied
Keyword(s):  
High Performance ◽  
Sound Intensity ◽  
Acoustic Metamaterials ◽  
Noise Mitigation ◽  
Wing Membrane ◽  
Acoustic Metamaterial ◽  
Optical Metamaterials ◽  
Broadband Absorption ◽  
Unit Cells ◽  
Individual Contributions

Metamaterials assemble multiple subwavelength elements to create structures with extraordinary physical properties (1–4). Optical metamaterials are rare in nature and no natural acoustic metamaterials are known. Here, we reveal that the intricate scale layer on moth wings forms a metamaterial ultrasound absorber (peak absorption = 72% of sound intensity at 78 kHz) that is 111 times thinner than the longest absorbed wavelength. Individual scales act as resonant (5) unit cells that are linked via a shared wing membrane to form this metamaterial, and collectively they generate hard-to-attain broadband deep-subwavelength absorption. Their collective absorption exceeds the sum of their individual contributions. This sound absorber provides moth wings with acoustic camouflage (6) against echolocating bats. It combines broadband absorption of all frequencies used by bats with light and ultrathin structures that meet aerodynamic constraints on wing weight and thickness. The morphological implementation seen in this evolved acoustic metamaterial reveals enticing ways to design high-performance noise mitigation devices.

Noise Control of a Chamber Core Cylinder Using Cylindrical Helmholtz Resonators

2003 ◽  
Author(s):  
Deyu Li ◽  
Jeffrey S. Vipperman
Keyword(s):  
Resonant Frequency ◽  
Noise Level ◽  
Noise Control ◽  
Low Frequencies ◽  
Optimal Position ◽  
Cylindrical Structure ◽  
Helmholtz Resonators ◽  
Resonator Design ◽  
Frequency Calculation ◽  
Cavity Resonances

Previous investigations have determined that the noise transmission into a finite cylindrical structure at low frequencies is dominated by the cavity resonances. Therefore, noise control at the first several cavity resonances for a Chamber Core cylinder can significantly reduce the noise level at low frequencies inside the cylinder. This work explores the feasibility of noise control for the Chamber Core cylinder using cylindrical Helmholtz resonators. The targeted frequencies are the first four cavity resonances. Detailed considerations of the resonant frequency calculation, resonator design, and experimental verification are presented. The effects on the noise reduction spectrum of two closely spaced resonators are experimentally studied. The optimal position of the resonators is also discussed. The noise control results indicate that the Helmholtz resonators can significantly attenuate the noise level at the targeted frequency bands.

scholarly journals Low-Frequency, Open, Sound-Insulation Barrier by Two Oppositely Oriented Helmholtz Resonators

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1544
Author(s):  
Yi-Jun Guan ◽  
Yong Ge ◽  
Hong-Xiang Sun ◽  
Shou-Qi Yuan ◽  
Xiao-Jun Liu
Keyword(s):  
High Performance ◽  
Low Frequency ◽  
Single Layer ◽  
Sound Insulation ◽  
Architectural Acoustics ◽  
Frequency Sound ◽  
Helmholtz Resonators ◽  
Viscous Loss ◽  
Insulation Effect ◽  
Broadband Sound

In this work, a low-frequency, open, sound-insulation barrier, composed of a single layer of periodic subwavelength units (with a thickness of λ/28), is demonstrated both numerically and experimentally. Each unit was constructed using two identical, oppositely oriented Helmholtz resonators, which were composed of a central square cavity surrounded by a coiled channel. In the design of the open barrier, the distance between two adjacent units was twice the width of the unit, showing high-performance ventilation, and low-frequency sound insulation. A minimum transmittance of 0.06 could be observed around 121.5 Hz, which arose from both sound reflections and absorptions, created by the coupling of symmetric and asymmetric eigenmodes of the unit, and the absorbed sound energy propagating into the central cavity was greatly reduced by the viscous loss in the channel. Additionally, by introducing a multilayer open barrier, a broadband sound insulation was obtained, and the fractional bandwidth could reach approximately 0.19 with four layers. Finally, the application of the multilayer open barrier in designing a ventilated room was further discussed, and the results presented an omnidirectional, broadband, sound-insulation effect. The proposed open, sound-insulation barrier with the advantages of ultrathin thickness; omnidirectional, low-frequency sound insulation; broad bandwidth; and high-performance ventilation has great potential in architectural acoustics and noise control.

Multi-tonal low frequency noise control using Helmholtz resonators with complex cavity designs for aircraft cabin noise improvement

2021 ◽  
Vol 263 (2) ◽  
pp. 3975-3986
Author(s):  
Tenon Charly Kone ◽  
Sebastian Ghinet ◽  
Raymond Panneton ◽  
Thomas Dupont ◽  
Anant Grewal
Keyword(s):  
Noise Control ◽  
Transmission Loss ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Helmholtz Resonators ◽  
Resonance Frequencies

The noise control at multiple tonal frequencies simultaneously, in the low frequency range, is a challenge for aerospace, ground transportation and building industries. In the past few decades, various low frequency noise control solutions based on acoustic metamaterial designs have been presented in the literature. These solutions showed promising performance and are considered a better alternative to conventional sound insulation materials. In the present investigation, it was noticed that subdividing the cavity of a Helmholtz resonator allowed the control of multi-tonal noise at several resonance frequencies simultaneously and a shift of the resonance peaks towards the low frequencies. This paper proposes concepts of Helmholtz resonators with subdivided cavities to improve the sound transmission loss (STL) performance and simultaneously control the noise at several tonal frequencies. HRs with cylindrical shaped cavities were embedded in a layer of porous material. The STL of the metamaterial noise insulation configuration was predicted using serial and parallel assemblies of transfer matrices (TMM) incorporating a thermo-viscous-acoustic approach to accurately account for the viscous and thermal losses of acoustic wave propagation within the metamaterial. The STL calculated using the proposed TMM approach were observed to be in excellent agreement with the finite element method (FEM) numerical results.

Co-planar two-dimensional Metal-Insulator-Semiconductor Capacitor: Numerical study of the device electrostatics.

2017 ◽  
Author(s):  
Varun Bheemireddy
Keyword(s):  
Space Charge ◽  
High Performance ◽  
Numerical Study ◽  
2D Materials ◽  
Space Charge Density ◽  
Two Dimensional ◽  
Short Channel ◽  
Metal Insulator ◽  
Metal Insulator Semiconductor ◽  
New Family

The two-dimensional(2D) materials are highly promising candidates to realise elegant and e cient transistor. In the present letter, we conjecture a novel co-planar metal-insulator-semiconductor(MIS) device(capacitor) completely based on lateral 2D materials architecture and perform numerical study of the capacitor with a particular emphasis on its di erences with the conventional 3D MIS electrostatics. The space-charge density features a long charge-tail extending into the bulk of the semiconductor as opposed to the rapid decay in 3D capacitor. Equivalently, total space-charge and semiconductor capacitance densities are atleast an order of magnitude more in 2D semiconductor. In contrast to the bulk capacitor, expansion of maximum depletion width in 2D semiconductor is observed with increasing doping concentration due to lower electrostatic screening. The heuristic approach of performance analysis(2D vs 3D) for digital-logic transistor suggest higher ON-OFF current ratio in the long-channel limit even without third dimension and considerable room to maximise the performance of short-channel transistor. The present results could potentially trigger the exploration of new family of co-planar at transistors that could play a signi significant role in the future low-power and/or high performance electronics.<br>

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.

scholarly journals 2D MoS2 Encapsulated Silicon Nanopillar Array with High-Performance Light Trapping Obtained by Direct CVD Process

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 267
Author(s):  
Minyu Bai ◽  
Zhuoman Wang ◽  
Jijie Zhao ◽  
Shuai Wen ◽  
Peiru Zhang ◽  
...  
Keyword(s):  
Silicon Substrate ◽  
High Performance ◽  
Low Cost ◽  
Light Trapping ◽  
Incident Light ◽  
Single Layer ◽  
Chemical Vapor ◽  
Optoelectronic Device ◽  
Planar Silicon ◽  
Shortwave Infrared

Weak absorption remains a vital factor that limits the application of two-dimensional (2D) materials due to the atomic thickness of those materials. In this work, a direct chemical vapor deposition (CVD) process was applied to achieve 2D MoS2 encapsulation onto the silicon nanopillar array substrate (NPAS). Single-layer 2D MoS2 monocrystal sheets were obtained, and the percentage of the encapsulated surface of NPAS was up to 80%. The reflection and transmittance of incident light of our 2D MoS2-encapsulated silicon substrate within visible to shortwave infrared were significantly reduced compared with the counterpart planar silicon substrate, leading to effective light trapping in NPAS. The proposed method provides a method of conformal deposition upon NPAS that combines the advantages of both 2D MoS2 and its substrate. Furthermore, the method is feasible and low-cost, providing a promising process for high-performance optoelectronic device development.

Well-Aligned Graphene Oxide Nanosheets Decorated with Zinc Oxide Nanocrystals for High Performance Photocatalytic Application

2015 ◽  
Vol 14 (03) ◽  
pp. 1550007 ◽  
Author(s):  
K. Kaviyarasu ◽  
C. Maria Magdalane ◽  
E. Manikandan ◽  
M. Jayachandran ◽  
R. Ladchumananandasivam ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Graphene Oxide ◽  
High Performance ◽  
Chemical Reduction ◽  
Visible Region ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Graphene Oxides ◽  
X Ray ◽  
Nanoscale Structures

Graphene oxide (GO) nanosheets modified with zinc oxide nanocrystals were achieved by a green wet-chemical approach. As-obtained products were characterized by XRD, Raman spectra, XPS, HR-TEM, EDS, PL and Photocatalytic studies. XRD studies indicate that the GO nanosheet have the same crystal structure found in hexagonal form of ZnO . The enhanced Raman spectrum of 2D bands confirmed formation of single layer graphene oxides. The gradual photocatalytic reduction of the GO nanosheet in the GO : ZnO suspension of ethanol was studied by using X-ray photoelectron (XPS) spectroscopy. The nanoscale structures were observed and confirmed using high resolution transmission electron microscopy (HR-TEM). The evolution of the elemental composition, especially the various numbers of layers were determined from energy dispersive X-ray spectra (EDS). PL properties of GO : ZnO nanosheet were found to be dependent on the growth condition and the resultant morphology revealed that GO nanosheet were highly transparent in the visible region. The photocatalytic performance of GO : ZnO nanocomposites was performed under UV irradiation. Therefore, the ZnO nanocrystals in the GO : ZnO composite could be applied in gradual chemical reduction and consequently tuning the electrical conductivity of the graphene oxide nanosheet.

scholarly journals A Metawindow with Optimised Acoustic and Ventilation Performance

2021 ◽  
Vol 11 (7) ◽  
pp. 3168
Author(s):  
Gioia Fusaro ◽  
Xiang Yu ◽  
Zhenbo Lu ◽  
Fangsen Cui ◽  
Jian Kang
Keyword(s):  
Natural Ventilation ◽  
Noise Control ◽  
Fem Analysis ◽  
The Finite Element Method ◽  
Noise Mitigation ◽  
Acoustic Performance ◽  
Potential Applications ◽  
Ventilation Performance ◽  
Sound Reduction ◽  
Window Design

Crucial factors in window performance, such as natural ventilation and noise control, are generally conceived separately, forcing users to choose one over the other. To solve this dualism, this study aimed to develop an acoustic metamaterial (AMM) ergonomic window design to allow noise control without dependence on the natural ventilation duration and vice versa. First, the finite element method (FEM) was used to investigate the noise control performance of the acoustic metawindow (AMW) unit, followed by anechoic chamber testing, which also served as the validation of the FEM models. Furthermore, FEM analysis was used to optimise the acoustic performance and assess the ventilation potential. The numerical and experimental results exhibited an overall mean sound reduction of 15 dB within a bandwidth of 380 to 5000 Hz. A good agreement between the measured and numerical results was obtained, with a mean variation of 30%. Therefore, the AMW unit optimised acoustic performance, resulting in a higher noise reduction, especially from 50 to 500 Hz. Finally, most of the AMW unit configurations are suitable for natural ventilation, and a dynamic tuned ventilation capacity can be achieved for particular ranges by adjusting the window’s ventilation opening. The proposed designs have potential applications in building acoustics and engineering where natural ventilation and noise mitigation are required to meet regulations simultaneously.

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