Engineering three-dimensional labyrinthine fractal acoustic metamaterials with low-frequency multi-band sound suppression

2021 ◽  
Vol 149 (1) ◽  
pp. 308-319
Author(s):  
Xianfeng Man ◽  
Baizhan Xia ◽  
Zhen Luo ◽  
Jian Liu ◽  
Kun Li ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Sound Suppression ◽  
Multi Band

scholarly journals 3D Hilbert fractal acoustic metamaterials: low-frequency and multi-band sound insulation

2019 ◽  
Vol 52 (19) ◽  
pp. 195302 ◽  
Author(s):  
Xian-feng Man ◽  
Bai-zhan Xia ◽  
Zhen Luo ◽  
Jian Liu
Keyword(s):  
Low Frequency ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Multi Band

scholarly journals Band Gaps and Vibration Isolation of a Three-dimensional Metamaterial with a Star Structure

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3812 ◽  
Author(s):  
Heng Jiang ◽  
Mangong Zhang ◽  
Yu Liu ◽  
Dongliang Pei ◽  
Meng Chen ◽  
...  
Keyword(s):  
Band Gap ◽  
Vibration Isolation ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Mass Density ◽  
Three Dimensional ◽  
Low Frequency ◽  
Band Gaps ◽  
Acoustic Metamaterials ◽  
Star Structure

Elastic metamaterials have promising applications in wave control and vibration isolation, due to their extraordinary characteristics, e.g., negative Poisson ratio, band gaps, effective negative mass density and effective negative modulus. How to develop new functional metamaterials using a special structure has always been a hot topic in this field. In this study, a three-dimensional (3D) star structure is designed to construct metamaterials with both negative static and dynamic properties. The results show that the 3D star structure formed a wide band gap at lower frequency and had a negative Poisson’s ratio. Different from conventional acoustic metamaterials, the main physical mechanism behind the low-frequency band gap of the 3D star structure is the resonance mode formed by the bending deformation of each rib plate, which made it easier to achieve effective isolation of low-frequency elastic waves with a low mass density. In addition, many structural parameters of the 3D star structure can be modulated to effectively adjust the band gap frequency by changing the angle between the concave nodes and aspect ratio. This study provides a new way to design the 3D acoustic metamaterials and develop the lightweight vibration isolation devices.

scholarly journals Study on broadband low-frequency sound insulation of multi-channel resonator acoustic metamaterials

AIP Advances ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 045321
Author(s):  
Chi Xu ◽  
Hui Guo ◽  
Yinghang Chen ◽  
Xiaori Dong ◽  
Hongling Ye ◽  
...  
Keyword(s):  
Low Frequency ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Frequency Sound

Tunable underwater acoustic metamaterials via quasi-Helmholtz resonance: From low-frequency to ultra-broadband

2021 ◽  
Vol 118 (7) ◽  
pp. 071904
Author(s):  
Mingyu Duan ◽  
Chenlei Yu ◽  
Fengxian Xin ◽  
Tian Jian Lu
Keyword(s):  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Underwater Acoustic ◽  
Helmholtz Resonance

scholarly journals Evolution of a narrow-band spectrum of random surface gravity waves

2003 ◽  
Vol 478 ◽  
pp. 1-10 ◽  
Author(s):  
KRISTIAN B. DYSTHE ◽  
KARSTEN TRULSEN ◽  
HARALD E. KROGSTAD ◽  
HERVÉ SOCQUET-JUGLARD
Keyword(s):  
Three Dimensional ◽  
Low Frequency ◽  
Three Dimensions ◽  
Band Spectrum ◽  
Nls Equation ◽  
Random Surface ◽  
Narrow Bandwidth ◽  
Quasi Stationary State ◽  
The Stability ◽  
Three Dimensional Simulations

Numerical simulations of the evolution of gravity wave spectra of fairly narrow bandwidth have been performed both for two and three dimensions. Simulations using the nonlinear Schrödinger (NLS) equation approximately verify the stability criteria of Alber (1978) in the two-dimensional but not in the three-dimensional case. Using a modified NLS equation (Trulsen et al. 2000) the spectra ‘relax’ towards a quasi-stationary state on a timescale (ε2ω0)−1. In this state the low-frequency face is steepened and the spectral peak is downshifted. The three-dimensional simulations show a power-law behaviour ω−4 on the high-frequency side of the (angularly integrated) spectrum.

Comprehensive design analysis of a 3D printed sensor for readiness assessment applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tanushree Agarwal ◽  
Fatemeh Rahmani ◽  
Ishtique Zaman ◽  
Federico Gasbarri ◽  
Keivan Davami ◽  
...  
Keyword(s):  
Sensor Array ◽  
Short Circuit ◽  
Three Dimensional ◽  
Low Frequency ◽  
Optimal Placement ◽  
Chemical Plants ◽  
Readiness Assessment ◽  
Element Analysis ◽  
Content Type ◽  
Flexible Antenna

Purpose This paper aims to develop a comprehensive model of a magnetic sensor array that will be operational for a multitude of electric components in continuous and nonintrusive condition monitoring (CM) or in readiness assessment (RA) applications. Design/methodology/approach A universal nonintrusive model of a flexible antenna array is introduced to monitor and identify failures in electric machine drives. An adjustable sensor is designed to serve as a RA for a vast range of electrical elements in a typical power system by capturing the low-frequency radiated magnetic fields. Findings The optimal placement of the most sensitive radiated fields from several components has been discovered in this case study, enabling the detection of healthy current flow throughout. Thereafter, the short-circuit investigation, representing faulty situations, is implemented and compared with healthy cases. Practical implications This sensing technique can be used for nonintrusive CM of components that are out of reach and cannot have the sensor to be held around it such as components in offshore winds, wind energy generation and power and chemical plants. Originality/value The results are provided for three commonly used machines with a single sensor array with numerous settings. The three dimensional (3 D) finite element analysis is applied in the structuring of the sensor, detection of the optimum location and recognition of faults in the machines. Finally, based on the setup design, 3 D printing is used for the construction of the sensor array. Thus, the sensor array with fault detection avoids major component failures and increases system reliability/resiliency.

scholarly journals Spiral Sound Wave Transducer Based on the Longitudinal Vibration

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3674 ◽  
Author(s):  
Wei Lu ◽  
Yu Lan ◽  
Rongzhen Guo ◽  
Qicheng Zhang ◽  
Shichang Li ◽  
...  
Keyword(s):  
Sound Wave ◽  
Longitudinal Vibration ◽  
Three Dimensional ◽  
Low Frequency ◽  
Sound Field ◽  
Field Measurements ◽  
Sound Waves ◽  
Underwater Sound ◽  
Three Dimensional Finite Element ◽  
Wave Transducer

A spiral sound wave transducer comprised of longitudinal vibrating elements has been proposed. This transducer was made from eight uniform radial distributed longitudinal vibrating elements, which could effectively generate low frequency underwater acoustic spiral waves. We discuss the production theory of spiral sound waves, which could be synthesized by two orthogonal acoustic dipoles with a phase difference of 90 degrees. The excitation voltage distribution of the transducer for emitting a spiral sound wave and the measurement method for the transducer is given. Three-dimensional finite element modeling (FEM)of the transducer was established for simulating the vibration modes and the acoustic characteristics of the transducers. Further, we fabricated a spiral sound wave transducer based on our design and simulations. It was found that the resonance frequency of the transducer was 10.8 kHz and that the transmitting voltage resonance was 140.5 dB. The underwater sound field measurements demonstrate that our designed transducer based on the longitudinal elements could successfully generate spiral sound waves.

Unsteady measurements in a separated and reattaching flow

1984 ◽  
Vol 144 ◽  
pp. 13-46 ◽  
Author(s):  
N. J. Cherry ◽  
R. Hillier ◽  
M. E. M. P. Latour
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Separation Bubble ◽  
Scale Up ◽  
Three Dimensional ◽  
Low Frequency ◽  
Vortical Structures ◽  
Large Scale Structures ◽  
Bubble Length ◽  
Low Frequency Motion

Measurements of fluctuating pressure and velocity, together with instantaneous smoke-flow visualizations, are presented in order to reveal the unsteady structure of a separated and reattaching flow. It is shown that throughout the separation bubble a low-frequency motion can be detected which appears to be similar to that found in other studies of separation. This effect is most significant close to separation, where it leads to a weak flapping of the shear layer. Lateral correlation scales of this low-frequency motion are less than the reattachment length, however; it appears that its timescale is about equal to the characteristic timescale for the shear layer and bubble to change between various shedding phases. These phases were defined by the following observations: shedding of pseudoperiodic trains of vortical structures from the reattachment zone, with a characteristic spacing between structures of typically 60% to 80% of the bubble length; a large-scale but irregular shedding of vorticity; and a relatively quiescent phase with the absence of any large-scale shedding structures and a significant ‘necking’ of the shear layer downstream of reattachment.Spanwise correlations of velocity in the shear layer show on average an almost linear growth of spanwise scale up to reattachment. It appears that the shear layer reaches a fully three-dimensional state soon after separation. The reattachment process does not itself appear to impose an immediate extra three-dimensionalizing effect upon the large-scale structures.

scholarly journals Demultiplexing Infrasound Phonons With Tunable Magnetic Lattices

2020 ◽  
Vol 7 ◽  
Author(s):  
Audrey A. Watkins ◽  
Osama R. Bilal
Keyword(s):  
Self Assembly ◽  
Small Volume ◽  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Propagation Characteristics ◽  
Low Frequencies ◽  
Experimental Realization ◽  
Nonlinear Properties ◽  
Potential Applications ◽  
Low Frequency Waves

Controlling infrasound signals is crucial to many processes ranging from predicting atmospheric events and seismic activities to sensing nuclear detonations. These waves can be manipulated through phononic crystals and acoustic metamaterials. However, at such ultra-low frequencies, the size (usually on the order of meters) and the mass (usually on the order of many kilograms) of these materials can hinder its potential applications in the infrasonic domain. Here, we utilize tunable lattices of repelling magnets to guide and sort infrasound waves into different channels based on their frequencies. We construct our lattices by confining meta-atoms (free-floating macroscopic disks with embedded magnets) within a magnetic boundary. By changing the confining boundary, we control the meta-atoms’ spacing and therefore the intensity of their coupling potentials and wave propagation characteristics. As a demonstration of principle, we present the first experimental realization of an infrasound phonon demultiplexer (i.e., guiding ultra-low frequency waves into different channels based on their frequencies). The realized platform can be utilized to manipulate ultra-low frequency waves, within a relatively small volume, while utilizing negligible mass. In addition, the self-assembly nature of the meta-atoms can be key in creating re-programmable materials with exceptional nonlinear properties.

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