ACOUSTIC BAND GAP FORMATION IN TWO-DIMENSIONAL LOCALLY RESONANT SONIC CRYSTALS COMPRISED OF HELMHOLTZ RESONATORS

2009 ◽  
Vol 23 (20n21) ◽  
pp. 4234-4243 ◽  
Author(s):  
L. CHALMERS ◽  
D. P. ELFORD ◽  
F. V. KUSMARTSEV ◽  
G. M. SWALLOWE
Keyword(s):  
Band Gap ◽  
Experimental Testing ◽  
Wide Band ◽  
Band Gaps ◽  
Gap Formation ◽  
Helmholtz Resonators ◽  
Multiple Resonance ◽  
Resonance Band ◽  
Sonic Crystal ◽  
Sonic Crystals

We present a new type of sonic crystal technology offering a novel method of achieving broad acoustic band gaps. The proposed design of a locally resonating sonic crystal (LRSC) is constructed from "C"-shaped Helmholtz resonators as opposed to traditional solid scattering units. This unique construction enables a two band gap system to be generated in which the first — a Bragg type band gap, arises due to the periodic nature of the crystal, whilst the second gap results from resonance of the air column within the resonators. The position of this secondary band gap is found to be dependent upon the dimensions of the resonating cavity. The band gap formation is investigated theoretically using finite element methods, and confirmed through experimental testing. It is noted that the resonance band gaps detected cover a much broader frequency range (in the order of kHz) than has been achieved to date. In addition the possibility of overlapping such a wide band gap with the characteristic Bragg gap generated by the structure itself could yield gaps of even greater range. A design of sonic crystal is proposed, that comprises of several resonators with differing cavity sizes. Such a structure generates multiple resonance gaps corresponding to the various resonator sizes, which may be overlapped to form yet larger band gaps. This multiple resonance gap system can occur in two configurations. Firstly a simple mixed array can be created by alternating resonator sizes in the array and secondly using a system coined the Matryoshka (Russian doll) array in which the resonators are distributed inside one another. The proposed designs of LRSC's offer a real potential for acoustic shielding using sonic crystals, as both the size and position of the band gaps generated can be controlled. This is an application which has been suggested and investigated for several years with little progress. Furthermore the frequency region attenuated by resonance is unrelated to the crystals lattice constant, providing yet more flexibility in the design of such devices.

scholarly journals ACOUSTIC BAND GAP FORMATION IN METAMATERIALS

2010 ◽  
Vol 24 (25n26) ◽  
pp. 4935-4945 ◽  
Author(s):  
D. P. ELFORD ◽  
L. CHALMERS ◽  
F. KUSMARTSEV ◽  
G. M. SWALLOWE
Keyword(s):  
Band Gap ◽  
Lattice Constant ◽  
Low Frequency ◽  
Band Gaps ◽  
Gap Formation ◽  
Individual Band ◽  
Resonance Band ◽  
Frequency Regime ◽  
Sonic Crystal ◽  
The Individual

We present several new classes of metamaterials and/or locally resonant sonic crystal that are comprised of complex resonators. The proposed systems consist of multiple resonating inclusion that correspond to different excitation frequencies. This causes the formation of multiple overlapped resonance band gaps. We demonstrate theoretically and experimentally that the individual band gaps achieved, span a far greater range (≈ 2kHz) than previously reported cases. The position and width of the band gap is independent of the crystal's lattice constant and forms in the low frequency regime significantly below the conventional Bragg band gap. The broad envelope of individual resonance band gaps is attractive for sound proofing applications and furthermore the devices can be tailored to attenuate lower or higher frequency ranges, i.e., from seismic to ultrasonic.

Analysis of the interaction of helmholtz resonators in periodic acoustic metamaterials depending on its orientation with the acoustic source.

2021 ◽  
Vol 263 (6) ◽  
pp. 215-226
Author(s):  
David Ramírez ◽  
Sergio Castiñeira-Ibáñez ◽  
Jose Maria Bravo-Plana-Sala ◽  
Juan Vicente Sánchez-Pérez ◽  
Rubén Picó
Keyword(s):  
Experimental Testing ◽  
Helmholtz Resonator ◽  
Simulation Models ◽  
Acoustic Metamaterials ◽  
New Materials ◽  
Acoustic Source ◽  
Helmholtz Resonators ◽  
Sonic Crystal ◽  
Environmental Acoustics ◽  
Sonic Crystals

Acoustic screens based on sonic crystals constitute one of the most promising technological bets of recent years in the field of environmental acoustics. Sonic crystals are defined as new materials formed by arrays of acoustic scatterers embedded in air. The design of these screens is made using powerful simulation models that provide reliable results without the need of expensive experimental testing. This project applies the finite elements method in order to analise an acoustic barrier that includes (Helmholtz) resonators in its scatterers, and studies the interference of the sonic crystal with the effect of the Helmholtz resonator, depending on its orientation with the acoustic source.

Numerical study for increasement of low frequency sound insulation of double-panel structure using sonic crystals with distributed Helmholtz resonators

2019 ◽  
Vol 33 (14) ◽  
pp. 1950138
Author(s):  
Myong-Jin Kim
Keyword(s):  
Free Space ◽  
Transmission Loss ◽  
Numerical Study ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Sound Insulation ◽  
The Finite Element Method ◽  
Helmholtz Resonators ◽  
Sonic Crystal ◽  
Sonic Crystals

Numerical simulations of the sound transmission loss (STL) of a double-panel structure (DPS) with sonic crystal (SC) comprised of distributed local resonators are presented. The Local Resonant Sonic Crystal (LRSC) consists of “C”-shaped Helmholtz resonator columns with different resonant frequencies. The finite element method is used to calculate the STL of such a DPS. First, the STLs of LRSC in free space and the DPS with LRSC are calculated and compared. It is shown that the sound insulations of the local resonators inserted in the double panel are higher than that in free space for the same size of the SCs and the same number of columns. Next, STL of the DPS in which the SC composed of three columns of local resonators having the same outer and inner diameters but different slot widths are calculated, and a reasonable arrangement order is determined. Finally, the soundproofing performances of DPS with distributed LRSC are compared with the case of insertion of general cylindrical SC for SC embedded in glass wool and not. The results show that the sound insulation of the DPS can be significantly improved in the low frequency range while reducing the total mass without increasing the thickness.

Parametric Study on Rectangular Sonic Crystal

2012 ◽  
Vol 152-154 ◽  
pp. 281-286 ◽  
Author(s):  
Arpan Gupta ◽  
Kian Meng Lim ◽  
Chye Heng Chew
Keyword(s):  
Band Gap ◽  
Periodic Structure ◽  
Parametric Study ◽  
Sound Propagation ◽  
Periodic Structures ◽  
Sound Attenuation ◽  
Experimental Results ◽  
Center Frequency ◽  
Sonic Crystal ◽  
Sonic Crystals

Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

Band Gap Formation in Composite Models With Quasi-Random Fiber Arrangements

2005 ◽  
Author(s):  
Shashidhar Patil ◽  
Liang-Wu Cai
Keyword(s):  
Band Gap ◽  
Large Scale ◽  
Composite Plates ◽  
Two Dimensions ◽  
Band Gaps ◽  
Gap Formation ◽  
Statistical Parameters ◽  
Composite Models ◽  
Gap Characteristics ◽  
Primary Band

Large-scale deterministic simulations are performed in order to observe the band gap formation in composite models having quasi-random fiber arrangements. Composite plates are modeled in two-dimensions with various unidirectional fiber arrangements. The quasi-random fiber arrangements can be qualified as essentially regular with slight randomness. Simulation results are compared with the corresponding case of ideally regular fiber arrangement. The most interesting observation is that the slight randomness in the fiber arrangements enhances the band gap phenomenon by introducing a few secondary band gaps adjacent to the primary band gap. An attempt is made to relate the band gap characteristics to the statistical parameters of fiber arrangements.

scholarly journals Unusual Blueshifting of Optical Band Gap of CdS Nanocrystals through a Chemical Bath Deposition Method

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Shu Qing Yuan ◽  
Peng Fei Ji ◽  
Yong Li ◽  
Yue Li Song ◽  
Feng Qun Zhou
Keyword(s):  
Band Gap ◽  
Chemical Bath Deposition ◽  
Optical Band Gap ◽  
Quantum Effect ◽  
Wide Band ◽  
Chemical Bath Deposition Method ◽  
Band Gaps ◽  
Deposition Method ◽  
Defect States ◽  
Cds Nanocrystals

CdS nanocrystals are synthesized through a chemical bath deposition method. After annealing, these nanocrystals are enlarged according to Scherrer’s formula. Small nanocrystals display wide band gaps as a result of the quantum effect experienced by nanocrystals of a certain size. However, the absorption edge and green and red emissions of annealed CdS nanocrystals show obvious blueshift compared with the as-grown ones. After annealing, the intensity ratio of these green and red emissions increases, which indicated that the defect states are reduced. Therefore, the improvement in crystalline quality and the reduced strain contribute to the unusual blueshifting of the optical band gap and of the green and red emissions.

UNIFORM BENDING EFFECT ON ELECTRONIC PROPERTIES OF BORON NITRIDE NANORIBBONS: A COMPUTATIONAL INVESTIGATION

Nano LIFE ◽  
2012 ◽  
Vol 02 (02) ◽  
pp. 1240005
Author(s):  
YUNLONG LIAO ◽  
ZHONGFANG CHEN
Keyword(s):  
Boron Nitride ◽  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Wide Band ◽  
Band Gaps ◽  
Computational Investigation ◽  
Wide Band Gap ◽  
Bending Effect ◽  
Boron Nitride Nanoribbons

First-principles computations were performed to investigate the uniform bending effect on the electronic properties of armchair boron nitride nanoribbons (aBNNRs) with experimentally obtained width. For both bare and hydrogen-terminated aBNNRs, the band gaps only slightly depend on the uniform bending. The insensitivity of the band structures of BNNRs to the uniform bending makes them ideal materials when their wide band gap character is desired.

Transition of wide-band gap semiconductor h-BN(BN)/P heterostructure via single-atom-embedding

2020 ◽  
Vol 8 (28) ◽  
pp. 9755-9762 ◽  
Author(s):  
Itsuki Miyazato ◽  
Tanveer Hussain ◽  
Keisuke Takahashi
Keyword(s):  
Boron Nitride ◽  
Band Gap ◽  
First Principles ◽  
Wide Band ◽  
Band Gaps ◽  
Single Atom ◽  
First Principles Calculations ◽  
Optoelectronic Materials ◽  
Wide Band Gap

The band gaps in boron nitride/phosphorene (h-BN/P) heterostructures are investigated by single-atom-embedding via first principles calculations. The modified heterostructures are potential optoelectronic materials with tunable band gaps.

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