Refractive Acoustic Devices for Airborne Sound

Cervera, Francisco; Sánchis, Lorenzo; Sánchez‐Pérez, J. V.; Martínez‐Sala, R.; Rubio, Constanza; Meseguer, F.; López, Carmelo; Caballero, David; Sánchez‐Dehesa, José

doi:10.1103/physrevlett.88.023902

Cited by 273 publications

(208 citation statements)

References 15 publications

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“…In a recent paper, 6 we resolved that question by using the rigorous MST to derive the Berryman mass density expression, and explained the experimental data by Cervera et al 7 on that basis. Thus, we have established unambiguously that the effective dynamic mass density can be different from the static one at the long wavelength ͑or zero frequency͒ limit.…”

Section: Recapitulationmentioning

confidence: 99%

“…However, when the impedance mismatch is relatively moderate, e.g., when the mass density contrast is small, then the effective dynamic mass density yields the VAMD. That is, VAMD 7. Blue ͑dark gray͒ indicates low field intensity, and yellow ͑light gray͒ indicates high field intensity.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

“…7 Here, the frequency of sound is 600 Hz and the Al cylinders have a maximum diameter of 3.175 cm, with a hexagonal lattice constant of 6.35 cm. The wavelength of sound in air, 57 cm, is thus much larger than either the cylinder diameter or the lattice constant.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

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Effective dynamic mass density of composites

et al. 2007

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The static mass density of a composite is simply the volume average of its constituents' densities. The dynamic density of a composite is defined to be the quantity that enters in evaluating the elastic wave velocity at the low-frequency limit. We show through a rigorous derivation that the effective dynamic mass density of an inhomogeneous mixture can differ from its static counterpart when the composite matrix is a fluid or, more generally, when there are relative motions between the matrix and inclusions. Derivation of the dynamic mass density expressions, involving taking the long wavelength limit of the rigorous multiple scattering theory, is detailed for the two-dimensional case. We also extend the effective dynamic mass density expression to finite frequencies where there can be low-frequency resonances. By combining both analytical and numerical approaches, negative or complex dynamic mass density is obtained for composites that contain a sufficient fraction of locally resonant inclusions. Thus, the dynamic mass density of a composite can differ from the static ͑volume-averaged͒ value even in the zero frequency limit, although both must be positive in that limit. Negative or complex dynamic mass density can occur at finite frequencies. These two results are shown to be consistent with each other, as well as related by the same underlying physics. As by-products of our rigorous derivation, we also verify some prior known results on the effective elastic moduli of composites.

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Section: Recapitulationmentioning

confidence: 99%

Section: Comparison With Experimental Datamentioning

confidence: 99%

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Effective dynamic mass density of composites

et al. 2007

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“…This holds for various types of waves over a large range of length scales: from electrons in atomic crystals 1 and light in photonic crystals [2][3][4] to acoustic waves in sonic crystals 5 . The eigenstates of these waves are best described with a band structure, which represents the relation between the energy and the wavevector (k).…”

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confidence: 99%

Ultrafast evolution of photonic eigenstates in k-space

et al. 2007

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Periodic structures have a large influence on propagating waves. This holds for various types of waves over a large range of length scales: from electrons in atomic crystals 1 and light in photonic crystals 2-4 to acoustic waves in sonic crystals 5 . The eigenstates of these waves are best described with a band structure, which represents the relation between the energy and the wavevector (k). This relation is usually not straightforward: owing to the imposed periodicity, bands are folded into every Brillouin zone, inducing splitting of bands and the appearance of bandgaps. As a result, exciting phenomena such as negative refraction 6,7 , autocollimation of waves 8,9 and low group velocities 10-12 arise. k-space investigations of electronic eigenstates have already yielded new insights into the behaviour of electrons at surfaces and in novel materials [13][14][15][16] . However, for a complete characterization of a structure, an understanding of the mutual coupling of eigenstates is also essential. Here, we investigate the propagation of light pulses through a photonic crystal structure using a near-field microscope 17,18 . Tracking the evolution of the photonic eigenstates in both k-space and time allows us to identify individual eigenstates and to uncover their dynamics and coupling to other eigenstates on femtosecond timescales even when co-localized in real space and time.

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“…These hidden degrees of freedom are particularly important because the effective macroscopic properties of an acoustic metamaterial can be significantly different than those of the constituent microstructural elements. When there is open flow through the structure, such as a sonic crystal lattice [18,19] or transmission-line arrangement of Helmholtz resonators [20], it is relatively straightforward to extract effective properties experimentally due to the relatively low acoustic impedance.…”

Section: Introductionmentioning

confidence: 99%

Aerogel as a Soft Acoustic Metamaterial for Airborne Sound

et al. 2016

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Soft acoustic metamaterials utilizing mesoporous structures have been proposed recently as a means for tuning the overall effective properties of the metamaterial and providing better coupling to the surrounding air. In this paper, the use of silica aerogel is examined theoretically and experimentally as part of a compact soft acoustic metamaterial structure, which enables a wide range of exotic effective macroscopic properties to be demonstrated, including negative density, density near zero, and nonresonant broadband slow-sound propagation. Experimental data are obtained on the effective density and sound speed using an air-filled acoustic impedance tube for flexural metamaterial elements, which have been investigated previously only indirectly due to the large contrast in acoustic impedance compared to that of air. Experimental results are presented for silica aerogel arranged in parallel with either one or two acoustic ports and are in very good agreement with the theoretical model.

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Refractive Acoustic Devices for Airborne Sound

Cited by 273 publications

References 15 publications

Effective dynamic mass density of composites

Effective dynamic mass density of composites

Ultrafast evolution of photonic eigenstates in k-space

Aerogel as a Soft Acoustic Metamaterial for Airborne Sound

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