Broadband low-frequency acoustic absorber based on a metaporous composite

2022 ◽  
Author(s):  
Jia-Hao Xu ◽  
Xing-Feng Zhu ◽  
Di-Chao Chen ◽  
Qi Wei ◽  
Da-Jian Wu
Keyword(s):  
Acoustic Waves ◽  
High Efficiency ◽  
Low Frequency ◽  
Frequency Noise ◽  
Sound Waves ◽  
Broadband Absorption ◽  
Trapped Mode ◽  
Potential Applications ◽  
Simulation And Experiment ◽  
Interest In Research

Abstract Broadband absorption of low-frequency sound waves via a deep subwavelength structure is of great and ongoing interest in research and engineering. Here, we numerically and experimentally present a design of a broadband low-frequency absorber based on an acoustic metaporous composite (AMC). The AMC absorber is constructed by embedding a single metamaterial resonator into a porous layer. The finite element simulations show that a high absorption (absorptance A > 0.8) can be achieved within a broad frequency range (from 290 Hz to 1074 Hz), while the thickness of AMC is 1/13 of the corresponding wavelength at 290 Hz. The broadband and high-efficiency performances of the absorber are attributed to the coupling between the two resonant absorptions and the trapped mode. A good agreement between the numerical simulation and experiment is obtained. Moreover, the high broadband absorption can be maintained under random incident acoustic waves. The proposed absorber provides potential applications in low-frequency noise reduction especially when limited space is demanded.

scholarly journals Noise Properties of Graphene-Polymer Thick-Film Resistors

2017 ◽  
Vol 24 (4) ◽  
pp. 585-590 ◽  
Author(s):  
Krzysztof Mleczko ◽  
Piotr Ptak ◽  
Zbigniew Zawiślak ◽  
Marcin Słoma ◽  
Małgorzata Jakubowska ◽  
...  
Keyword(s):  
Thick Film ◽  
Room Temperature ◽  
Low Frequency ◽  
Frequency Noise ◽  
Potential Applications ◽  
Noise Measurements ◽  
Manufacturing Technologies ◽  
Main Component ◽  
Resistance Fluctuations ◽  
Parameter Values

AbstractGraphene is a very promising material for potential applications in many fields. Since manufacturing technologies of graphene are still at the developing stage, low-frequency noise measurements as a tool for evaluating their quality is proposed. In this work, noise properties of polymer thick-film resistors with graphene nano-platelets as a functional phase are reported. The measurements were carried out in room temperature. 1/f noise caused by resistance fluctuations has been found to be the main component in the specimens. The parameter values describing noise intensity of the polymer thick-film specimens have been calculated and compared with the values obtained for other thick-film resistors and layers used in microelectronics. The studied polymer thick-film specimens exhibit rather poor noise properties, especially for the layers with a low content of the functional phase.

Light-Driven Acoustic Band Gap Based on Metal Nanospheres

2009 ◽  
Vol 74 ◽  
pp. 17-20 ◽  
Author(s):  
Jiu Hui Wu ◽  
Boris Luk’yanchuk ◽  
Hua Ling Chen ◽  
Ai Qun Liu
Keyword(s):  
Band Gap ◽  
Acoustic Waves ◽  
Van Der Waals ◽  
Low Frequency ◽  
Optical Force ◽  
Potential Applications ◽  
Incident Laser Intensity ◽  
Metal Materials ◽  
Optical Distribution ◽  
Gap Width

In this paper, light-driven acoustic band gap is presented by considering two metal nanospheres illuminated simultaneously by laser and acoustic waves. The interaction between the photonics and phonons is investigated through optical distribution force, van der Waals distribution force, and acoustic pressure upon these nanospheres. Based on the optical force and van der Waals force, the acoustic form functions for the metal nanoaggregates with different optical intensity are calculated, and the light-driven acoustics band gap at low frequency band has been found. It is shown that the band gap width can be widened with increasing the incident laser intensity, or by using proper metal materials and background media. This could provide potential applications in optical nanoswitches and acoustical filters.

Young’s Modulus Detection for Ultra-Thin Film by LSAWs Technique with Wavelet and FIR Filter De-Noising

2011 ◽  
Vol 301-303 ◽  
pp. 623-628 ◽  
Author(s):  
Xing Meng Shan ◽  
Xia Xiao ◽  
Yuan Sun
Keyword(s):  
Young’S Modulus ◽  
Acoustic Waves ◽  
Young's Modulus ◽  
Surface Acoustic Waves ◽  
Low Frequency ◽  
Experimental System ◽  
Fir Filter ◽  
Least Square ◽  
Frequency Noise ◽  
Young’S Moduli

Laser-generated surface acoustic waves (LSAWs) technique is a feasible method to determine the Young’s modulus of thin films. The raw surface acoustic wave (SAW) signals detected from the experimental system are often contaminated by external noises. A novel de-noising method is proposed in this paper with wavelet and FIR filter. The wavelet threshold de-noising is essential to reduce the high frequency noise components in the raw SAW signals, while FIR filter can remove the useless low frequency noises. The useful bandwidth of the detected signal ranges from 50 to 190 MHz. Young’s modulus of the detected samples can be obtained by matching the experimental dispersive curves with the theoretical calculated ones via an improved least square fitting method. The Young’s moduli of four low dielectric constant (low-k) samples detected in the measurement are 7.1, 6.8, 1.1 and 1.0 GPa, respectively.

Flexibly guiding of acoustic waves by one-dimensional sonic crystal with omnidirectional bandgap

2015 ◽  
Vol 29 (28) ◽  
pp. 1550193 ◽  
Author(s):  
Hai-Long He ◽  
Shi-Liang Ou-Yang ◽  
Zhaojian He ◽  
Ke Deng ◽  
Heping Zhao
Keyword(s):  
Numerical Simulations ◽  
Crystal Structures ◽  
Acoustic Waves ◽  
High Efficiency ◽  
Wide Frequency Range ◽  
Sound Waves ◽  
Frequency Range ◽  
Bending Angle ◽  
One Dimensional ◽  
Sonic Crystal

An acoustic waveguide based on the omnidirectional reflection of one-dimensional (1D) sonic crystal (sc) is designed to realize the flexible guiding of sound waves. Numerical simulations indicate that high-efficiency transmission can be achieved at arbitrary bending angle and over a wide frequency range. Moreover, flexible waveguide branches can also be easily constructed by introducing more crystal structures into the waveguides. Owing to its designing flexibility, this waveguide would be very useful in various integrated applications based on SCs.

Study on low frequency sound insulation characteristic of thin acoustic black hole

2021 ◽  
pp. 2150198
Author(s):  
Xiao Lian ◽  
Shengsheng Wang ◽  
Maolin Liu ◽  
Songhui Nie ◽  
Jinfeng Peng ◽  
...  
Keyword(s):  
Black Hole ◽  
Acoustic Waves ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Insulation ◽  
Focusing Effect ◽  
Frequency Sound ◽  
Leading Role ◽  
Potential Applications ◽  
Energy Focusing

We use numerical and experimental methods to investigate the low frequency sound insulation characteristic of designed thin acoustic black hole (ABH). The numerical results show that the sound energy focusing effect plays a leading role in low frequency sound insulation of designed ABH, and the reflection at the edge of ABH is the main reason of sound insulation in medium and high frequencies. Experimental results display that the Sound Transmission Loss (STL) of the designed ABH is higher than 30 dB below 700 Hz, which shows that the isolated acoustic waves are more than 95%. The low frequency sound insulation performance of proposed ABHs is much better than the traditional acoustic materials, which has great potential applications for low frequency sound insulation.

scholarly journals Microwave Emission from Flaring Magnetic Loops

1980 ◽  
Vol 86 ◽  
pp. 173-176
Author(s):  
Loukas Vlahos
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Magnetic Energy ◽  
Low Frequency ◽  
Impulsive Phase ◽  
High Energy ◽  
Microwave Emission ◽  
Sound Waves ◽  
Charge Imbalance ◽  
Ion Acoustic

We discuss the microwave emission from a flaring loop (Spicer 1977). In particular we examine the following question: What will be the characteristics of the radio emission at centimeter wavelengths from a small compact flaring loop (average plasma density ne ≃ 1010 cm−3, average magnetic field at the footpoint of the loop Bℓ ≃ 500 gauss and Bt ≃ 100 gauss at the top of the loop and length of the loop, L = 109 cm), when the mechanism which pumps magnetic energy into the plasma in the form of heating and/or electron acceleration satisfies the following conditions. a. The magnetic energy is released in a small volume, (the energy release volume (ERV)), compared to the volume of the loop, and the rate at which magnetic energy is transformed into plasma energy is faster than the energy losses from the same volume. This causes a local enhancement of the temperature by as much as one or two orders of magnitude above the coronal temperature. b). The bulk of the energy released goes into heating the plasma and heats primarily the electrons (Te > Ti). Using these two assumptions one can easily show (Brown, Melrose and Spicer 1979, Vlahos and Papadopoulos 1979) that the high energy electrons in the tail of the velocity distribution in the ERV will instantaneously run away from this volume, and the resulting charge imbalance between the ERV and its surroundings (which still have average coronal temperatures ~ 106 K), will drive a return current, with velocity VD. When VD reaches the value of the local sound speed Cs ≃ 107 cm/sec low frequency ion acoustic waves will be excited at the interface of the ERV and its surroundings. It has been shown that the heat flow along the magnetic field lines is greatly reduced due to the presence of ion-acoustic turbulence (cf. Manheimer 1977). The bulk of the electrons in the ERV have electron-wave collision times **τw << 10–100 sec, longer than the impulsive phase of the flare. But since τw ~ v3 for those electrons with velocity v > ve (see Rudakov and Korablev 1966) the electrons in the tail will not “see” the ion sound waves and will stream freely towards the chromosphere.

scholarly journals The scattering analysis of trifurcated waveguide involving structural discontinuities

2019 ◽  
Vol 11 (7) ◽  
pp. 168781401982928 ◽  
Author(s):  
Touqeer Nawaz ◽  
Muhammad Afzal ◽  
Rab Nawaz
Keyword(s):  
Cross Sections ◽  
Acoustic Waves ◽  
Active Noise Control ◽  
Low Frequency ◽  
Solution Procedure ◽  
Control Measures ◽  
Frequency Noise ◽  
Normal Velocity ◽  
Field Potentials ◽  
Matching Technique

The present article highlights the acoustic waves scattering in a trifurcated waveguide containing compressible fluid together with step discontinuities and change of bounding material properties. The study is important because of its applications in active noise control measures, especially used to control the low-frequency noise and related vibrations. The governing boundary value problem is solved by using the mode-matching technique. The solution is developed for the analysis of symmetric, uniform, and non-uniform cross-sections. The solution procedure begins by determining the expanded form of field potentials in various duct regions of the waveguide. Then, the pressures and the normal velocity modes across the waveguide regions are matched at interface. The energy flux against frequency and various duct configurations is plotted. The solution is validated altogether through the apposite analytical and numerical results.

Underwater metastructure with broadband sound absorption capability in low-frequency range above 20 Hz

2020 ◽  
pp. 2150039
Author(s):  
Ruihao Zhang ◽  
Yifan Song ◽  
Hong Hou ◽  
Nansha Gao
Keyword(s):  
Absorption Coefficient ◽  
Acoustic Waves ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Rubber Matrix ◽  
Conical Cavity ◽  
Propagation Law ◽  
Potential Applications ◽  
Metal Disk

We present an underwater metastructure with excellent sound absorption effect below 50 Hz. The periodic metastructure unit consists of a conical cavity, rubber matrix, and two metal disks. FEM results show that, in the range of 20–300 Hz, the proposed metastructure demonstrates the excellent sound absorption within 279 Hz bandwidth when the reference absorption coefficient is considered to be 0.5. Displacement vibration diagrams illustrate the addition of two layers of metal disks break the propagation law of acoustic wave in rubber matrix. An anti-phase motion of the rubber matrix emerges due to the presence of the metal disks, then consumes the energy of incident acoustic waves. The geometric parameters of lattice constant [Formula: see text], the thickness [Formula: see text], and the height [Formula: see text] of the upper metal disk are positively correlated with the sound absorption coefficient, while the upper radius [Formula: see text] and the height [Formula: see text] of the conical cavity are negatively correlated with the sound absorption coefficient. The novel design presented in this study could have the potential applications in the realization of an acoustic underwater anechoic layer.

Transmission control of acoustic metasurface with dumbbell-shaped double-split hollow sphere

2020 ◽  
Vol 34 (33) ◽  
pp. 2050386
Author(s):  
Yibao Dong ◽  
Yuanbo Wang ◽  
Jianxiang Sun ◽  
Changlin Ding ◽  
Shilong Zhai ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Simple Structure ◽  
Negative Refraction ◽  
Hollow Spheres ◽  
Complex Structures ◽  
Sound Waves ◽  
Large Size ◽  
Audible Frequency ◽  
Potential Applications ◽  
Focusing Lens

Complex structures, large size and limited manipulation of acoustic waves are the problems that restrict the development of acoustic metasurfaces. Here, we report a transmission-type acoustic metasurface based on local resonance mechanism, which is composed of meta-atomic units called dumbbell-shaped double-split hollow spheres (DSDSHS). This metasurface with subwavelength scale has the advantage of simple structure and easy preparation, and can realize the full manipulation of sound waves. Negative refraction with different transmission angles and high intensity plate focusing lens are realized in the air environment of audible frequency. The proposed metasurface has potential applications in the miniaturization and integration of sound transmission and sound energy collection, opening a new opportunity for manipulation of acoustic wavefront.

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