An acoustic absorbing metamaterial with multi-Helmholtz resonators at low-frequency underwater

An ultra-thin waterborne acoustic metamaterial (AM), which is made of steel and composed of multi-Helmholtz resonators (MHRs), is proposed to achieve perfect sound absorption at low frequencies, which are generated around the resonance mode. The average surface acoustic impedance of the metamaterial is almost perfectly matched with water impedance under the action of resonance among the HRs, thus the perfect sound absorption is achieved. The case of two resonators is taken as an example to verify the design idea. By adjusting HRs’ sizes in simulation, the sound absorption coefficient reaches 99.6% at low frequency of 2740 Hz with ultra-thin thickness less than [Formula: see text]. The abnormal physical properties of AMs are often accompanied by abnormal effective material parameters, which turn to be negative near the perfect sound absorption through inversion calculation. The HRs proposed are simple to fabricate, mechanically stable, and convenient to couple with other resonators to achieve low-frequency broadband sound absorption.

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Highly Efficient Low‐Frequency Broadband Sound Absorption with a Composite Hybrid Metasurface

Advanced Engineering Materials ◽

10.1002/adem.202100791 ◽

2021 ◽

Author(s):

Qingxuan Liang ◽

Yutao Wu ◽

Peiyao Lv ◽

Jin He ◽

Fuyin Ma ◽

...

Keyword(s):

Sound Absorption ◽

Low Frequency ◽

Highly Efficient ◽

Broadband Sound

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A multilayer microperforated panel prototype for broadband sound absorption at low frequencies

Applied Acoustics ◽

10.1016/j.apacoust.2018.11.014 ◽

2019 ◽

Vol 146 ◽

pp. 134-144 ◽

Cited By ~ 15

Author(s):

F. Bucciarelli ◽

G.P. Malfense Fierro ◽

M. Meo

Keyword(s):

Sound Absorption ◽

Low Frequencies ◽

Broadband Sound

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Simulation research on low frequency sound absorption of monostable metamaterials

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1614 ◽

2021 ◽

Vol 263 (6) ◽

pp. 648-652

Author(s):

Tuo Xing ◽

Xianhui Li ◽

Xiaoling Gai ◽

Zenong Cai ◽

Xiwen Guan

Keyword(s):

Magnetic Field ◽

Finite Element ◽

Theoretical Model ◽

Finite Element Simulation ◽

Sound Absorption ◽

Magnetic Force ◽

Low Frequency ◽

Low Frequencies ◽

Element Simulation ◽

Simulation Results

The monostable acoustic metamaterial is realized by placing a flexible panel with a magnetic proof mass in a symmetric magnetic field. The theoretical model of monostable metamaterials has been proposed. The method of finite element simulation is used to verify the theoretical model. The magnetic force of the symmetrical magnetic field is simplified as the relationship between force and displacement, acting on the mass. The simulation results show that as the external magnetic force increases, the peak sound absorption shifts to low frequencies. The theoretical and finite element simulation results are in good agreement.

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Hybrid acoustic metamaterial as super absorber for broadband low-frequency sound

Scientific Reports ◽

10.1038/srep43340 ◽

2017 ◽

Vol 7 (1) ◽

Cited By ~ 58

Author(s):

Yufan Tang ◽

Shuwei Ren ◽

Han Meng ◽

Fengxian Xin ◽

Lixi Huang ◽

...

Keyword(s):

Energy Dissipation ◽

Absorption Coefficient ◽

Sound Absorption ◽

Low Frequency ◽

Functional Materials ◽

Theoretical Method ◽

Acoustic Metamaterials ◽

Mechanical Stiffness ◽

Acoustic Metamaterial ◽

Frequency Sound

Abstract A hybrid acoustic metamaterial is proposed as a new class of sound absorber, which exhibits superior broadband low-frequency sound absorption as well as excellent mechanical stiffness/strength. Based on the honeycomb-corrugation hybrid core (H-C hybrid core), we introduce perforations on both top facesheet and corrugation, forming perforated honeycomb-corrugation hybrid (PHCH) to gain super broadband low-frequency sound absorption. Applying the theory of micro-perforated panel (MPP), we establish a theoretical method to calculate the sound absorption coefficient of this new kind of metamaterial. Perfect sound absorption is found at just a few hundreds hertz with two-octave 0.5 absorption bandwidth. To verify this model, a finite element model is developed to calculate the absorption coefficient and analyze the viscous-thermal energy dissipation. It is found that viscous energy dissipation at perforation regions dominates the total energy consumed. This new kind of acoustic metamaterials show promising engineering applications, which can serve as multiple functional materials with extraordinary low-frequency sound absorption, excellent stiffness/strength and impact energy absorption.

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

Micromachines ◽

10.3390/mi12121544 ◽

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.

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