The use of slow waves to design simple sound absorbing materials

Groby, Jean‐Philippe; Huang, Weichun; Lardeau, Alexandre; Aurégan, Yves

doi:10.1063/1.4915115

Cited by 107 publications

(74 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This last type of metamaterials [10][11][12] makes use of its strong dispersion for generating slow-sound conditions inside the material and, therefore, drastically decreasing frequency of the absorption peaks. Hence, the structure thickness becomes deeply sub-wavelength.…”

Section: Jun 2016mentioning

confidence: 99%

Ultra-thin metamaterial for perfect and quasi-omnidirectional sound absorption

Jiménez

Huang

Romero‐García

et al. 2016

Applied Physics Letters

Self Cite

296

172

View full text Add to dashboard Cite

Using the concepts of slow sound and of critical coupling, an ultra-thin acoustic metamaterial panel for perfect and omnidirectional absorption is theoretically and experimentally conceived in this work. The system is made of a rigid panel with a periodic distribution of thin closed slits, the upper wall of which is loaded by Helmholtz Resonators (HRs). The presence of resonators produces a slow sound propagation shifting the resonance frequency of the slit to the deep sub-wavelength regime (λ/88). By controlling the geometry of the slit and the HRs, the intrinsic visco-thermal losses can be tuned in order to exactly compensate the energy leakage of the system and fulfill the critical coupling condition to create the perfect absorption of sound in a large range of incidence angles due to the deep subwavelength behavior. * noe.jimenez@univ-lemans.fr 1 arXiv:1606.07776v1 [physics.class-ph] Jun 2016The ability to perfectly absorb an incoming wave field in a sub-wavelength material is advantageous for several applications in wave physics as energy conversion [1], time reversal technology [2], coherent perfect absorbers [3] or soundproofing [4] among others. The solution of this challenge requires to solve a complex problem: reducing the geometric dimensions of the structure while increasing the density of states at low frequencies and finding the good conditions to match the impedance to the background medium.A successful approach for increasing the density of states at low frequencies with reduced dimensions is the use of metamaterials. Recently, several possibilities based on these systems have been proposed to design sound absorbing structures which can present simultaneously sub-wavelength dimensions and strong acoustic absorption. One strategy to design these sub-wavelength systems consists of using space-coiling structures [5,6]. Another way is to use sub-wavelength resonators as membranes [4,7] or Helmholtz resonators (HRs) [8,9].Recently, a new type of sub-wavelength metamaterials based on the concept of slow sound propagation have been used to the same purpose. This last type of metamaterials [10][11][12] makes use of its strong dispersion for generating slow-sound conditions inside the material and, therefore, drastically decreasing frequency of the absorption peaks. Hence, the structure thickness becomes deeply sub-wavelength. All of these structures, however, while they bring potentially solutions to reduce the geometric dimensions, face the challenge of impedance mismatch to the background medium.The interaction of an incoming wave with a lossy resonant structure, in particular the impedance matching with the background field, is one of the most studied process in the field of wave physics [1][2][3]. These open systems, at the resonant frequency, are characterized by both the leakage rate of energy (i.e., the coupling of the resonant elements with the propagating medium), and the intrinsic losses of the resonator. The balance between the leakage and the losses activates the condition of critic...

show abstract

Section: Jun 2016mentioning

confidence: 99%

Ultra-thin metamaterial for perfect and quasi-omnidirectional sound absorption

Jiménez

Huang

Romero‐García

et al. 2016

Applied Physics Letters

Self Cite

296

172

View full text Add to dashboard Cite

show abstract

“…Recently the use of slow sound material has been proposed by Groby et al (2015). By decreasing the effective compressibility in a tube (Aur egan and Pagneux, 2015), the effective sound velocity and, as a consequence, the material thickness can be drastically reduced.…”

Section: Introductionmentioning

confidence: 99%

Low frequency sound attenuation in a flow duct using a thin slow sound material

Aurégan¹,

Farooqui²,

Groby³

2016

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

We present a thin subwavelength material that can be flush mounted to a duct and which gives a large wide band attenuation at remarkably low frequencies in air flow channels. To decrease the material thickness, the sound is slowed in the material using folded side branch tubes. The impedance of the material is compared to the optimal value, which differs greatly from the characteristic impedance. In particular, the viscous and thermal effects have to be very small to have high transmission losses.Grazing flow on this material increases the losses at the interface between the flow and the material.

show abstract

“…These specific materials are artificial structures composed of an arrangement of resonant unit cells-smaller than the characteristic wavelength-that present effective properties not observed in the materials that compose the structure. Examples of such absorbers are metaporous materials [6][7][8][9], metamaterials composed of membrane-type resonators [10][11][12][13], Helmholtz resonators (HRs) [13][14][15][16], and quarter-wavelength resonators (QWRs) [4,[17][18][19]. These last types of metamaterials [4,[15][16][17][18]] make use of strong dispersion, giving rise to slow-sound propagation inside the material.…”

Section: Introductionmentioning

confidence: 99%

Iridescent Perfect Absorption in Critically-Coupled Acoustic Metamaterials Using the Transfer Matrix Method

et al. 2017

View full text Add to dashboard Cite

Abstract:The absorption performance of a locally-reacting acoustic metamaterial under oblique incidence is studied. The metamaterial is composed of a slotted panel, each slit being loaded by an array of Helmholtz resonators. The system is analytically studied using the transfer matrix method, accounting for the viscothermal losses both in the resonator elements and in the slits, allowing the representation of the reflection coefficient in the complex frequency plane. We show that by tuning the geometry of the metamaterial, perfect absorption peaks can be obtained on demand at selected frequencies and different angles of incidence. When tilting the incidence angle, the peaks of perfect absorption are shifted in frequency, producing an acoustic iridescence effect similar to the optic iridescence achieved by incomplete band gap. Effectively, we show that in this kind of locally-reacting metamaterial, perfect and omnidirectional absorption for a given frequency is impossible to achieve because the metamaterial impedance does not depend on the incidence angle (i.e., the impedance is a locally reacting one). The system is interpreted in the complex frequency plane by analysing the trajectories of the zeros of the reflection coefficient. We show that the trajectories of the zeros do not overlap under oblique incidence, preventing the observation of perfect and omnidirectional absorption in locally reacting metamaterials. Moreover, we show that for any locally resonant material, the absorption in diffuse field takes a maximal value of 0.951, which is achieved by a material showing perfect absorption for an incidence angle of 50.34 degrees.

show abstract

The use of slow waves to design simple sound absorbing materials

Cited by 107 publications

References 23 publications

Ultra-thin metamaterial for perfect and quasi-omnidirectional sound absorption

Ultra-thin metamaterial for perfect and quasi-omnidirectional sound absorption

Low frequency sound attenuation in a flow duct using a thin slow sound material

Iridescent Perfect Absorption in Critically-Coupled Acoustic Metamaterials Using the Transfer Matrix Method

Contact Info

Product

Resources

About