Widening, transition and coalescence of local resonance band gaps in multi-resonator acoustic metamaterials: From unit cells to finite chains

Abstract Elastic and acoustic metamaterials can sculpt dispersion of waves through resonances. In turn, resonances can give rise to negative effective properties, usually localized around the resonance frequencies, which support band gaps at subwavelength frequencies (i.e., below the Bragg-scattering limit). However, the band gaps width correlates strongly with the resonators’ mass and volume, which limits their functionality in applications. Trampoline phenomena have been numerically and experimentally shown to broaden the operational frequency ranges of two-dimensional, pillar-based metamaterials through perforation. In this work, we demonstrate trampoline phenomena in lightweight and planar lattices consisting of arrays of Archimedean spirals in unit cells. Spiral-based metamaterials have been shown to support different band gap opening mechanisms, namely, Bragg-scattering, local resonances and inertia amplification. Here, we numerically analyze and experimentally realize trampoline phenomena in planar metasurfaces for different lattice tessellations. Finally, we carry out a comparative study between trampoline pillars and spirals and show that trampoline spirals outperform the pillars in lightweight, compactness and operational bandwidth.

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

Modern Physics Letters B ◽

10.1142/s0217984916501116 ◽

2016 ◽

Vol 30 (08) ◽

pp. 1650116 ◽

Cited By ~ 3

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.

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MODIFICATION OF CASIMIR FORCES DUE TO BAND GAPS IN PERIODIC STRUCTURES

International Journal of Modern Physics A ◽

10.1142/s0217751x02010145 ◽

2002 ◽

Vol 17 (06n07) ◽

pp. 798-803 ◽

Cited By ~ 7

Author(s):

C. VILLARREAL ◽

R. ESQUIVEL-SIRVENT ◽

G. H. COCOLETZI

Keyword(s):

Density Of States ◽

Casimir Force ◽

Periodic Structures ◽

Local Density ◽

Band Gaps ◽

Basic Unit ◽

Local Density Of States ◽

Casimir Forces ◽

Unit Cells ◽

The Difference

The Casimir force between inhomogeneous slabs that exhibit a band-like structure is calculated. The slabs are made of basic unit cells each made of two layers of different materials. As the number of unit cells increases the Casimir force between the slabs changes, since the reflectivity develops a band-like structure characterized by frequency regions of high reflectivity. This is also evident in the difference of the local density of states between free and boundary distorted vacuum, that becomes maximum at frequencies corresponding to the band gaps. The calculations are restricted to vacuum modes with wave vectors perpendicular to the slabs.

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Insertion loss of periodic cylindrical shells with helical slit

Noise Control Engineering Journal ◽

10.3397/1/376920 ◽

2021 ◽

Vol 69 (3) ◽

pp. 199-208

Author(s):

Karisma Mohapatra ◽

Dibya Prakash Jena

Keyword(s):

Band Structure ◽

Insertion Loss ◽

Cylindrical Shells ◽

Slit Width ◽

Sharp Peak ◽

Acoustic Attenuation ◽

High Frequencies ◽

Local Resonance ◽

Resonance Band

We propose periodic shells with helical slit to overcome the lacuna in periodic C scatterers, where the first Bragg band is considerably reduced on increasing width of the slit. The key discovery of this research indicates that, by changing the upright slit of the C scatterers to helical slits, larger insertion loss (IL) is achieved around the first Bragg band without compromising the local resonance band. Comparing the performance of periodic shells without slit or cylindrical scatterers, it is found that IL becomes larger at first Bragg band. The pitch, thickness of the shell and width of helical slit can be altered to adjust the resonance of the proposed shells. On decreasing the pitch or increasing the slit width, the resonance band shifts toward high frequencies without much alteration in acoustic attenuation of bandwidth. Additionally, below threshold pitch, the said peak merges with first Bragg band and broadens with prominent IL. The calculated band structure authenticates the bandwidth of the first Bragg band, and the additional sharp peak in IL can be attributed to local resonance of the periodic scatterers.

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