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.

Acoustic Magnifying Lens Based on Compact Non-Dispersive Spiral Metamaterial Array

2021 ◽  
Author(s):  
Li Xiang ◽  
Li Jian ◽  
Huang Xinjing
Keyword(s):  
Periodic Structures ◽  
Pressure Amplitude ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Alternate Route ◽  
Nondestructive Detection ◽  
Natural Materials ◽  
Compact Size ◽  
New Strategy ◽  
Focus Point

Abstract Acoustic magnifying lenses are utilized in a diversity of applications, from nondestructive detection of damages in materials to biomedical imaging. Acoustic metamaterials (MMs) provide powerful control over sound waves by using periodic structures made from natural materials. Existing acoustic meta-lens are commonly associated with designing dispersive metamaterial or connect with local resonator, thus resulting in inevitable deformity of waveforms. Although the four-blade spiral MMs has non-dispersive properties, how to further improve the transmission and reduce the manufacturing difficulty in a compact size is important to construction of a meta-lens. We propose a single-blade spiral metamaterial, which has higher transmission and non-dispersion properties. Based on this meta-unit, we designed and manufactured a meta-lens with the ability to amplify sound signals at the focus point. Different from previous research, the meta-lens is established by periodic meta-helicoid unit and presents great focusing ability while maintaining a compact volume. We show, both theoretically and experimentally, the thin flat acoustic magnifier can turn normally incident signals focusing on the prescribed point and augmenting pressure amplitude about three times. Moreover, the diameter of each element is only 10 mm, and the thickness of the meta-lens is 48mm. Our new strategy may offer an alternate route to the design of novel meta-lens and devices for acoustic application in the future.

scholarly journals Bilayer ventilated labyrinthine metasurfaces with high sound absorption and tunable bandwidth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiayuan Du ◽  
Yuezhou Luo ◽  
Xinyu Zhao ◽  
Xiaodong Sun ◽  
Yanan Song ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Air Flow ◽  
Single Layer ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Sound Barrier ◽  
Free Air ◽  
Relative Bandwidth ◽  
Wide Range ◽  
High Sound

AbstractThe recent advent of acoustic metamaterials offers unprecedented opportunities for sound controlling in various occasions, whereas it remains a challenge to attain broadband high sound absorption and free air flow simultaneously. Here, we demonstrated, both theoretically and experimentally, that this problem can be overcome by using a bilayer ventilated labyrinthine metasurface. By altering the spacing between two constituent single-layer metasurfaces and adopting asymmetric losses in them, near-perfect (98.6%) absorption is achieved at resonant frequency for sound waves incident from the front. The relative bandwidth of absorption peak can be tuned in a wide range (from 12% to 80%) by adjusting the open area ratio of the structure. For sound waves from the back, the bilayer metasurface still serves as a sound barrier with low transmission. Our results present a strategy to realize high sound absorption and free air flow simultaneously, and could find applications in building acoustics and noise remediation.

Locally resonant periodic structures with low-frequency band gaps

2013 ◽  
Vol 114 (3) ◽  
pp. 033532 ◽  
Author(s):  
Zhibao Cheng ◽  
Zhifei Shi ◽  
Y. L. Mo ◽  
Hongjun Xiang
Keyword(s):  
Frequency Band ◽  
Periodic Structures ◽  
Low Frequency ◽  
Band Gaps

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.

Acoustic manipulation of fractal metamaterials with negative properties and near-zero densities

2021 ◽  
Author(s):  
Guanghua Wu ◽  
Yibo Ke ◽  
Lin Zhang ◽  
Meng Tao
Keyword(s):  
High Potential ◽  
Experimental Results ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Acoustic Device

Abstract Acoustic metamaterials have high potential in diverse applications, including acoustic cloaking, sound tunneling, wavefront reshaping, and sound insulation. In the present study, new metamaterials consisting of spatial coiled units are designed and fabricated to manipulate sound waves in the range 0-1600 Hz. The effective acoustic properties and band diagrams are studied. The simulation and experimental results demonstrate that the metamaterials provide an effective and feasible approach to design acoustic device such as sound cloaking and insulators.

scholarly journals Gradient index phononic crystals and metamaterials

Nanophotonics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 685-701 ◽  
Author(s):  
Yabin Jin ◽  
Bahram Djafari-Rouhani ◽  
Daniel Torrent
Keyword(s):  
Refractive Index ◽  
Wave Propagation ◽  
Acoustic Waves ◽  
Effective Properties ◽  
Periodic Structures ◽  
Phononic Crystals ◽  
Ray Theory ◽  
Acoustic Metamaterials ◽  
Propagation Of Waves ◽  
At Will

AbstractPhononic crystals and acoustic metamaterials are periodic structures whose effective properties can be tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible to locally change the properties of a finite crystal in such a way that it results in an effective gradient of the refractive index. In such case the propagation of waves can be accurately described by means of ray theory, and different refractive devices can be designed in the framework of wave propagation in inhomogeneous media. In this paper we review the different devices that have been studied for the control of both bulk and guided acoustic waves based on graded phononic crystals.

A Controlled Pneumatic Actuation System

1965 ◽  
Author(s):  
Theodore T. Hadeler ◽  
Thomas P. Carey
Keyword(s):  
Pneumatic Actuation ◽  
Actuation System
Sign in / Sign up

Export Citation Format

Share Document