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.

scholarly journals Numerical Evaluation of Sound Attenuation Provided by Periodic Structures

2013 ◽  
Vol 38 (4) ◽  
pp. 503-516 ◽  
Author(s):  
Mário Martins ◽  
Luís Godinho ◽  
Luís Picado-Santos
Keyword(s):  
Periodic Structures ◽  
Traffic Noise ◽  
Fundamental Solutions ◽  
Sound Attenuation ◽  
Method Of Fundamental Solutions ◽  
Noise Sources ◽  
Noise Abatement ◽  
Acoustic Performance ◽  
Sonic Crystals ◽  
Different Sources

Abstract The use of periodic structures as noise abatement devices has already been the object of considerable research seeking to understand its efficiency and see to what extent they can provide a functional solu- tion in mitigating noise from different sources. The specific case of sonic crystals consisting of different materials has received special attention in studying the influence of different variables on its acoustic performance. The present work seeks to contribute to a better understanding of the behavior of these structures by implementing an approach based on the numerical method of fundamental solutions (MFS) to model the acoustic behavior of two-dimensional sonic crystals. The MFS formulation proposed here is used to evaluate the performance of crystals composed of circular elements, studying the effect of varying dimen- sions and spacing of the crystal elements as well as their acoustic absorption in the sound attenuation provided by the global structure, in what concerns typical traffic noise sources, and establishing some broad indications for the use of those structures.

Acoustical Study of a Lossy Gradient-Based Sonic Crystal Using Acoustic Beamforming

2021 ◽  
Author(s):  
Debasish Panda ◽  
Amiya Ranjan Mohanty
Keyword(s):  
Acoustic Waves ◽  
Periodic Structures ◽  
Fast Method ◽  
Fe Method ◽  
Helmholtz Resonators ◽  
Sonic Crystal ◽  
Gradient Based ◽  
Acoustical Study ◽  
Tunable Frequency ◽  
Sonic Crystals

Sonic crystals (SCs) are unique periodic structures designed to attenuate acoustic waves in tunable frequency bands known as bandgaps. Though previous works on conventional uniform SCs show good insertion loss (IL) inside the bandgaps, this work is focused on widening their bandgaps and achieving better IL inside the bandgaps by using a gradient-based sonic crystal (GBSC). The GBSC applies property gradient to the conventional SC array by varying its basic properties, i.e., the distance between the scatterers/resonators (lattice constant), and resonator dimensions between the columns and hence the name GBSC. The design of the GBSC is backed by the results of acoustic beamforming experiments conducted over the uniform SCs of hollow scatterers and Helmholtz resonators (HRs) having two-dimensional (2D) periodicity prepared by using Polyvinyl chloride (PVC) pipes without any property gradient and their respective 2D finite element (FE) studies. The experimental and FE simulation results of the uniform SCs were found to be in good agreement and therefore, the GBSC was modeled and analyzed using FE method considering the viscothermal losses inside the resonators. The results indicated that the property gradient improves both Bragg scattering and Helmholtz resonance compared to that of the uniform SCs and therefore, the GBSC exhibits wider attenuation gaps and higher attenuation levels. An array of 30 microphones was used to conduct acoustic beamforming experiments on the uniform SCs. Beamforming was found to be an advanced and fast method to perform quick measurements on the SCs.

Quasi-One-Dimensional Periodic Structure with Locally Resonant Band Gap

2005 ◽  
Vol 73 (1) ◽  
pp. 167-170 ◽  
Author(s):  
Gang Wang ◽  
Xisen Wen ◽  
Jihong Wen ◽  
Yaozong Liu
Keyword(s):  
Band Gap ◽  
Periodic Structure ◽  
Elastic Waves ◽  
Phononic Crystals ◽  
Experimental Results ◽  
Harmonic Oscillators ◽  
Dimensional Structure ◽  
Stiffness Ratio ◽  
One Dimensional ◽  
Two Factors

The propagation of longitudinal elastic waves in quasi one-dimensional structure consisting of harmonic oscillators periodically jointed on a slender beam is studied. Sub-frequency locally resonant band gap with highly asymmetric attenuation is observed in both theoretical and experimental results, and both results match well. The stiffness and mass ratios are found analytically as two factors that influence the actual attenuation in the band gap of the locally resonant phononic crystals. The study on the weights of the two factors shows that the stiffness ratio is the key one. Thus, the reason for the mismatch between the regions of the sharp attenuation and the theoretical band gap in the locally resonant phononic crystals is discovered.

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.

Harmonic and shock wave propagation in bistable periodic structure: Regularity, randomness, and tunability

2021 ◽  
pp. 107754632110310
Author(s):  
Encai Liu ◽  
Xin Fang ◽  
Jihong Wen
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Band Gap ◽  
Periodic Structure ◽  
Wave Amplitude ◽  
Multiple Equilibria ◽  
Energy Transport ◽  
Wave Attenuation ◽  
Periodic Structures ◽  
Shock Wave Propagation

Nonlinear periodic structures can present abundant nonlinear wave physics. The model consisting of periodic bistable oscillators (i.e., the bistable periodic structure) is essentially different from those nonlinear periodic systems consisting of monostable oscillators due to multiple equilibria in bistable periodic structure. Despite the extensive attention received, properties of harmonic and shock wave propagation in bistable periodic structure, especially the randomness and tunability behind regularity, have not been fully understood. This article reports the answers based on numerical method. We consider the varying trends of the band gap, vibration center, wave amplitude, and transmission and show their effects on energy transport. We find that the snap-through behavior always presents local intrinsic randomness with the regularity in whole, that is, it does not happen in sequence. For both harmonic and shock wave, most energy is localized inside the snap-through oscillators that changes the regularity for energy transport and is meaningful for shock wave protection. Bistable periodic structure can present very low-frequency and broadband wave attenuation by shifting the initial frequency of the band gap to nearly zero through tuning the wave amplitude to a critical value, which offers dynamic tunability. The damping and intensity of the shock pulse have significant effects on the shock wave propagation. This work provides guidance for the design and application of bistable periodic structure for elastic wave attenuation and shock wave protection.

scholarly journals Pseudospin-dependent Acoustic Topological Insulator by Sonic Crystals With Same Hexagonal Rods

2021 ◽  
Vol 9 ◽  
Author(s):  
Ding Jia ◽  
Shuai Gu ◽  
Shuai Jiang ◽  
Yong Ge ◽  
Shou-qi Yuan ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Sound Propagation ◽  
Numerical Realization ◽  
Topological Phase ◽  
Edge States ◽  
Topological Phase Transition ◽  
Band Inversion ◽  
Sonic Crystal ◽  
Zone Folding ◽  
Sonic Crystals

We report the experimental and numerical realization of a pseudospin-dependent acoustic topological insulator based on two sonic crystals constructed by the same regular hexagonal rods. Based on the zone folding mechanism, we obtain double Dirac cones with a four-fold deterministic degeneracy in the sonic crystal, and realize a band inversion and topological phase transition by rotating the rods. We observe the topologically protected one-way sound propagation of pseudospin-dependent edge states in a designed topological insulator composed of two selected sonic crystals with different rotation angles of the rods. Furthermore, we experimentally demonstrate the robustness of topological sound propagation against two types of defects, in which the edge states are almost immune to backscattering, and remain pseudospin-dependent characteristics. Our work provides a diverse route for designing tunable topological functional sound devices.

Excitation of Rotationally Periodic Structures

1979 ◽  
Vol 46 (4) ◽  
pp. 878-882 ◽  
Author(s):  
S. J. Wildheim
Keyword(s):  
Periodic Structure ◽  
Periodic Structures ◽  
Resonance Condition ◽  
Forced Response ◽  
Closed Ring ◽  
Additional Resonance ◽  
Rotationally Symmetric ◽  
Deformation Patterns ◽  
Frequency Diagram ◽  
Rotationally Periodic Structure

A rotationally periodic structure consists of a finite number of identical substructures forming a closed ring. The vibrational behavior of such structures is considered, especially the forced response due to a rotating force. It is known that for a rotationally symmetric structure, excited by a rotating force, resonance for the n nodal diameters mode is obtained when the corresponding natural frequency is ωn = nΩ, where Ω is the angular velocity of the force. This resonance condition also holds for a rotationally periodic structure. But then additional resonance possibilities exist, given by ωn = (kN ± n)Ω, where N is the number of substructures and k = 0, 1, 2,… These resonance conditions give a zigzag line in the nodal diameters versus frequency diagram, which here is introduced as the ZZENF diagram. The deformation patterns at the resonances are both forward and backward traveling waves.

Experimental Implementation of Negative Impedance Shunts on Periodic Structures

2009 ◽  
Author(s):  
Benjamin Beck ◽  
Kenneth A. Cunefare ◽  
Massimo Ruzzene ◽  
Manuel Collet
Keyword(s):  
Periodic Structures ◽  
Experimental Results ◽  
Periodic Array ◽  
Negative Capacitance ◽  
Experimental Implementation ◽  
Theoretical Predictions ◽  
Shunt Damping

Shunt damping of structures has been heavily researched, both passively and actively. Negative capacitance shunts actively control vibration on a structure and have been shown to obtain significant broadband suppression. The use of smaller piezoelectric patches, implemented in a periodic array, can alter the behavior of the control. Assorted shunt arrangements as well as circuit configurations will be investigated. Experimental results will be compared to theoretical predictions of shunt performance.

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