Multi-cavity locally resonant structure with the low frequency and broad band-gaps

This paper studies a novel kind of low-frequency broadband acoustic metamaterials with small size based on the mechanisms of negative mass density and multi-cavity coupling. The structure consists of a closed resonant cavity and an open resonant cavity, which can be equivalent to a homogeneous medium with effective negative mass density in a certain frequency range by using the parameter inversion method. The negative mass density makes the anti-resonance area increased, which results in broadened band gaps greatly. Owing to the multi-cavity coupling mechanism, the local resonances of the lower frequency mainly occur in the closed cavity, while the local resonances of the higher frequency mainly in the open cavity. Upon the interaction between the negative mass density and the multi-cavity coupling, there exists two broad band gaps in the range of 0–1800 Hz, i.e. the first-order band gap from 195 Hz to 660 Hz with the bandwidth of 465 Hz and the second-order band gap from 1157 Hz to 1663 Hz with the bandwidth of 506 Hz. The acoustic metamaterials with small size presented in this paper could provide a new approach to reduce the low-frequency broadband noises.

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Band gap analysis of a three-mass locally resonant structure

Noise & Vibration Worldwide ◽

10.1177/09574565211000411 ◽

2021 ◽

pp. 095745652110004

Author(s):

Preeti Gulia ◽

Arpan Gupta

Keyword(s):

Band Gap ◽

Gap Analysis ◽

Effective Properties ◽

Low Frequency ◽

Band Gaps ◽

Resonant Structure ◽

Resonant System ◽

Mass System ◽

Main Mass ◽

Mass Spring

A mass in a mass locally resonant system has been studied using a numerical and analytical method. This study is performed to compute the band gap and transmission coefficient of a mass–spring locally resonant system. A locally resonant structure is a periodic structure which exhibits negative effective properties in a certain frequency band and reveals band gaps below Bragg’s frequency. In this work, two substructures are attached with main mass so that the system will act as two masses in a mass system. It is found that the presented structure shows two band gaps below 500 Hz with negative effective properties. Addition of a third substructure with the main mass provides an additional band gap at low frequency. The position and width of band gaps can be tuned by changing the values of masses and stiffness.

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The Ultra-low Frequency and Broad Band Gaps Characteristics of Multilayer Composite Cylindrical Three-dimensional pentamode metamaterials

10.21203/rs.3.rs-969950/v1 ◽

2021 ◽

Author(s):

Chengxin Cai ◽

Xue Wang ◽

Qifu Wang ◽

Mingxing Li ◽

Guangchen He ◽

...

Keyword(s):

Acoustic Waves ◽

Broad Band ◽

Three Dimensional ◽

Engineering Application ◽

Low Frequency ◽

Single Mode ◽

Band Gaps ◽

Multilayer Composite ◽

Lattice Constants ◽

Mode Area

Abstract For three-dimensional pentamode metamaterials, it is of great significance to realize underwater ultra-low frequency acoustic wave control. Therefore, two types multilayer composite cylindrical three-dimensional pentamode metamaterials with ultra-low frequency and broad band gaps are proposed in this paper. By using pentamode metamaterials with lattice constants on the order of centimeters, the phononic band gaps below 60 Hz and the single-mode area below 30Hz can be obtained. Compared with asymmetrical double-cone locally resonant pentamode metamaterials, the lower edge frequency, relative bandwidth and figure of merit of the first phononic band gap can be reduced by up to 61.4%, 10.3% and 40.6%, respectively. It will provide reference and guidance for the engineering application of pentamode metamaterials in controlling the ultra-low frequency broadband acoustic waves, vibration and noise reduction.

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Multiple low-frequency broad band gaps generated by a phononic crystal of periodic circular cavity sandwich plates

Composite Structures ◽

10.1016/j.compstruct.2017.05.048 ◽

2017 ◽

Vol 176 ◽

pp. 294-303 ◽

Cited By ~ 11

Author(s):

Shan Jiang ◽

Hao Chen ◽

Longxiang Dai ◽

Hongping Hu ◽

Vincent Laude

Keyword(s):

Phononic Crystal ◽

Broad Band ◽

Low Frequency ◽

Band Gaps ◽

Sandwich Plates ◽

Circular Cavity

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Topological optimization of hierarchical honeycomb acoustic metamaterials for low-frequency extreme broad band gaps

Applied Acoustics ◽

10.1016/j.apacoust.2021.108579 ◽

2022 ◽

Vol 188 ◽

pp. 108579

Author(s):

Pei Sun ◽

Zhendong Zhang ◽

Hui Guo ◽

Ningning Liu ◽

Wenchao Jin ◽

...

Keyword(s):

Broad Band ◽

Low Frequency ◽

Band Gaps ◽

Topological Optimization ◽

Acoustic Metamaterials

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Numerical and Experimental Study of Flexural Wave Band Gaps of Periodical Locally-Resonant Beams With Suspended Separated Force and Moment Resonators

Volume 8: 27th Conference on Mechanical Vibration and Noise ◽

10.1115/detc2015-46033 ◽

2015 ◽

Author(s):

Hangyuan Lv ◽

Michael Yu Wang

Keyword(s):

Matrix Theory ◽

Periodic Structures ◽

Broad Band ◽

Low Frequency ◽

Flexural Vibration ◽

Band Gaps ◽

Flexural Wave ◽

Wave Band ◽

Vibration Transmittance ◽

Distance Parameter

In this paper, flexural vibration in a locally-resonant (LR) beam with periodically attached separated force and moment beam-like resonators is investigated theoretically and experimentally. The relationship between the distance parameter and the band structure of an Euler-Bernoulli beam with proposed locally resonators is provided using the transfer matrix theory. The frequency response functions of finite periodic systems are calculated with the finite element method over a range of different parameters of the resonators. Finally, we use LR beam specimens with separated force and moment resonators mounted on a free-free host beam for experimental measurements of the vibration transmittance. The experimental results show a good agreement with those of the theoretical and numerical except some small discrepancies at high frequencies. Our study confirms that the bandwidth of band-gaps will become wider with the increasing of the distance parameter until it reaches its peak, which provides an effective way for LR periodic structures with resonators to obtain broad band-gaps in low-frequency range, and makes the structure had potential applications in the control of vibration and wave propagation in flexural beams.

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The Low-Frequency Array (LOFAR): Opening a New Window on the Universe

Symposium - International Astronomical Union ◽

10.1017/s0074180900169591 ◽

2002 ◽

Vol 199 ◽

pp. 474-483

Author(s):

Namir E. Kassim ◽

T. Joseph W. Lazio ◽

William C. Erickson ◽

Patrick C. Crane ◽

R. A. Perley ◽

...

Keyword(s):

Angular Resolution ◽

Broad Band ◽

Low Frequency ◽

Electromagnetic Spectrum ◽

Interferometric Imaging ◽

Very Large Array ◽

Long Wavelength ◽

Calibration Techniques ◽

Long Baselines ◽

The Universe

Decametric wavelength imaging has been largely neglected in the quest for higher angular resolution because ionospheric structure limited interferometric imaging to short (< 5 km) baselines. The long wavelength (LW, 2—20 m or 15—150 MHz) portion of the electromagnetic spectrum thus remains poorly explored. The NRL-NRAO 74 MHz Very Large Array has demonstrated that self-calibration techniques can remove ionospheric distortions over arbitrarily long baselines. This has inspired the Low Frequency Array (LOFAR)—-a fully electronic, broad-band (15—150 MHz)antenna array which will provide an improvement of 2—3 orders of magnitude in resolution and sensitivity over the state of the art.

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The challenging SED of AP Librae

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312009532 ◽

2011 ◽

Vol 7 (S284) ◽

pp. 411-413 ◽

Cited By ~ 3

Author(s):

David Sanchez ◽

Berrie Giebels ◽

Pascal Fortin ◽

Keyword(s):

Spectral Energy Distribution ◽

Broad Band ◽

Low Frequency ◽

Theoretical Models ◽

Intermediate Frequency ◽

High Energy ◽

Spectral Energy ◽

Broad Band Emission ◽

Band Emission ◽

Bl Lac

AbstractMatching the broad-band emission of active galaxies with the predictions of theoretical models can be used to derive constraints on the properties of the emitting region and to probe the physical processes involved. AP Librae is the third low frequency peaked BL Lac (LBL) detected at very high energy (VHE, E>100GeV) by an Atmospheric Cherenkov Telescope; most VHE BL Lacs (34 out of 39) belong to the high-frequency and intermediate-frequency BL Lac classes (HBL and IBL). LBL objects tend to have a higher luminosity with lower peak frequencies than HBLs or IBLs. The characterization of their time-averaged spectral energy distribution is challenging for emission models such as synchrotron self-Compton (SSC) models.

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