Frequency band-selected one-way topological edge mode via acoustic metamaterials and metasurface

2021 ◽  
Vol 130 (8) ◽  
pp. 085101
Author(s):  
Xinpei Song ◽  
Tianning Chen ◽  
Rui Li
Keyword(s):  
Frequency Band ◽  
Acoustic Metamaterials ◽  
Edge Mode

Adjustable sound insulation frequency band through the combination of membrane-type acoustic metamaterial array

2021 ◽  
Vol 263 (1) ◽  
pp. 5869-5877
Author(s):  
Xiang Wu ◽  
TengLong Jiang ◽  
JianWang Shao ◽  
GuoMing Deng ◽  
Chang Jin
Keyword(s):  
Thin Films ◽  
Frequency Band ◽  
Transmission Loss ◽  
Structural Parameters ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Additional Mass ◽  
Acoustic Metamaterial ◽  
Material Parameters ◽  
Membrane Type

Membrane-type acoustic metamaterials are thin films or plates composed of periodic units with small additional mass. A large number of studies have shown that these metamaterials exhibit tunable anti-resonance, and their transmission loss values are much higher than the corresponding quality laws. At present, most researches on membrane-type acoustic metamaterials focus on the unit cell, and the sound insulation frequency band can only be adjusted by adjusting the structural parameters and material parameters. In this paper, two kinds of acoustic metamaterials with different structures are designed, which are the center placement of the mass and the eccentric placement of the mass.The two structures have different sound insulation characteristics. By designing different array combinations of acoustic metamaterials, the sound insulation peaks of different frequency bands are obtained. This paper studies the corresponding combination law, and effectively realizes the adjustable sound insulation frequency band.

scholarly journals Broadband impedance modulation via non-local acoustic metamaterials

2021 ◽  
Author(s):  
Zhiling Zhou ◽  
Sibo Huang ◽  
Dongting Li ◽  
Jie Zhu ◽  
Yong Li
Keyword(s):  
Frequency Band ◽  
Linear Time ◽  
Impedance Matching ◽  
Local Effect ◽  
Selective Absorption ◽  
Acoustic Metamaterials ◽  
Perfect Absorption ◽  
Impedance Modulation ◽  
Dual Functional ◽  
Non Local

Abstract Causality of linear time-invariant systems inherently defines the wave-matter interaction process in wave physics. This principle imposes strict constraints on the interfacial response of materials on various physical platforms. A typical consequence is that a delicate balance has to be struck between the conflicting bandwidth and geometric thickness when constructing a medium with desired impedance, which makes it challenging to realize broadband impedance modulation with compact structures. In pursue of improvement, the over-damped recipe and the reduced excessive response recipe are creatively presented in this work. As proof-of-concept demonstration, we construct a metamaterial with intensive mode density which supports strong non-locality over a frequency band from 320 Hz to 6400 Hz. Under the guidelines of the over-damped recipe and the reduced excessive response recipe, the metamaterial realizes impedance matching to air and exhibits broadband near-perfect absorption without evident impedance oscillation and absorption dips in the working frequency band. We further present a dual-functional design capable of frequency-selective absorption and reflection by concentrating the resonance modes in three frequency bands. Our research reveals the significance of the over-damped recipe and the strong non-local effect in broadband impedance modulation, which may open up avenues for constructing efficient artificial impedance boundaries for energy absorption and other wave manipulation.

scholarly journals Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1456 ◽  
Author(s):  
Reza Hedayati ◽  
Sandhya Lakshmanan
Keyword(s):  
Frequency Band ◽  
Open Space ◽  
Periodic Structures ◽  
Control Unit ◽  
Pressure Control ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Cavity Depth ◽  
Pneumatic Actuation ◽  
Actuation System

Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed- and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150–350 Hz to a frequency band of 300–600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies.

Viscoelastic multi-resonator mechanism for broadening low-frequency band-gap of acoustic metamaterials

2019 ◽  
Vol 86 (1) ◽  
pp. 10901 ◽  
Author(s):  
Hongxing Liu ◽  
Jiu Hui Wu
Keyword(s):  
Elastic Modulus ◽  
Band Gap ◽  
Frequency Band ◽  
Loss Modulus ◽  
Great Influence ◽  
Low Frequency ◽  
Band Gaps ◽  
Band Width ◽  
Acoustic Metamaterials ◽  
Practical Applications

In this paper, viscoelastic multi-resonator mechanism for broadening low-frequency band-gaps of acoustic metamaterials is investigated. Firstly, the metamaterial unit consists of dual-mass and dual-viscoelasticity is proposed which can generate multiple resonances to form multiple band-gaps, and further the broadened band-gaps are realized by modulating the effect of the viscoelasticity. Secondly, for the dual-viscoelasticity, the band-gaps and transmission spectrum under the cases of with the consistent and inconsistent viscoelasticity are calculated. Comparing with the consistent case, by adjusting the viscoelasticity in the inconsistent case, the storage modulus changes the fastest and obtains a smaller and a larger elastic modulus at the corresponding starting frequency and ending frequency of the band-gap, in which the band-gap can be broadened and shifted to the low frequency since the resonant frequency is determined by the elastic modulus, and for the loss modulus, it has little effects on the width of the band-gap, but has great influence on the transmission coefficient. Thirdly, by adjusting the inconsistent viscoelastic parameters based on the above rules, the band width is increased by 1.7 times (1.3 times for the absolute band width) than the consistent structure and the band-gap is shifted to the low frequency by 31% (about 345 Hz). The viscoelastic multi-resonator mechanism can be used to practical applications of viscoelastic metamaterials.

Multi-large low-frequency band gaps in a periodic hybrid structure

2016 ◽  
Vol 30 (08) ◽  
pp. 1650116 ◽  
Author(s):  
T. Wang ◽  
M. P. Sheng ◽  
H. B. Guo
Keyword(s):  
Frequency Band ◽  
Phononic Crystal ◽  
Low Frequency ◽  
Hybrid Structure ◽  
Band Gaps ◽  
Response Analysis ◽  
Acoustic Metamaterials ◽  
Frequency Range ◽  
Local Resonance ◽  
Small Series

A hybrid structure composed of a local resonance mass and an external oscillator is proposed in this paper for restraining the elastic longitudinal wave propagation. Theoretical model has been established to investigate the dispersion relation and band gaps of the structure. The results show that the hybrid structure can produce multi-band gaps wider than the multi-resonator acoustic metamaterials. It is much easier for the hybrid structure to yield wide and low band gaps by adjusting the mass and stiffness of the external oscillator. Small series spring constant ratio results in low-frequency band gaps, in which the external oscillator acts as a resonator and replaces the original local resonator to hold the band gaps in low frequency range. Compared with the one-dimensional phononic crystal (PC) lattice, a new band gap emerges in lower frequency range in the hybrid structure because of the added local resonance, which will be a significant assistance in low-frequency vibration and noise reduction. Further, harmonic response analysis using finite element method (FEM) has been performed, and results show that elastic longitudinal waves are efficiently forbidden within the band gaps.

Experimental Study of the Transmission Spectrum of a Sonic/Ultrasonic Acoustic Metamaterial

2016 ◽  
Author(s):  
Yanbo He ◽  
Jeffrey S. Vipperman
Keyword(s):  
Band Gap ◽  
Frequency Band ◽  
Transmission Spectrum ◽  
Physical Phenomenon ◽  
Experimental Studies ◽  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Acoustic Metamaterial ◽  
Potential Applications ◽  
Lower Frequency Band

Acoustic metamaterials have received much attention recently. In the past decades, countless structures have been studied for their novel physical phenomenon or potential applications. The goals of many of the works were to explore ways to enlarge the band gap, lower the band gap frequency, and/or generate greater attenuation of vibration. However, most of the work was limited to simulation, with experimental studies rarer. In this work, we would like to experimentally present the transmission spectrum of an acoustic metamaterial with a proposed structure called the coated double hybrid lattice (CDHL) [1]. The CDHL has both crystalline structure and local resonators, which provide high-frequency and low-frequency band gaps, respectively. A structure was fabricated and tested to experimentally determine the transmission spectrum. Both, a higher frequency band gap and a lower frequency band gap, were obtained. Vibration is clearly attenuated in the frequency range of 70–90 kHz. This is due to the Bragg scattering effect. At the same time, around the frequency of 4.8kHz, another band gap is observed which is attributed to local resonance. It turns out that our experimental results coincide with our previous simulation quite well.

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