Experimental realization of broadband acoustic omnidirectional absorber by homogeneous anisotropic metamaterials

Abstract

Analytical coupled vibroacoustic modeling of membrane-type acoustic metamaterials: Plate modelWe design a two-dimensional broadband acoustic omnidirectional absorber (AOA) simply comprising homogeneous anisotropic metamaterials to enlarge the absorption cross-section of a smaller core with matched acoustic impedance as the previous AOAs do, which generally involve complicated design of gradient-index or negative-index materials. Furthermore, AOAs with asymmetric/ large geometrics can be realized conveniently, which will otherwise require a complex redesign of parameters. The proposed scheme is also extendable to three-dimensional cases. An implementation using angularly distributed fins was demonstrated experimentally, showing the broadband functionality of the designed absorber. Such metamaterial-based acoustic absorbers may have potential applications in various fields such as acoustic energy concentration, noise control, etc. V C 2015 AIP Publishing LLC. [http://dx.

Viscothermal Effects in a Two-Dimensional Acoustic Black Hole: A Boundary Element Approach

“…The classical analogues of the quantum hole effect are topics of increasing interest in physics. The photonic black-hole (PBH) [1][2][3] and the acoustic black hole (ABH) [4][5][6][7][8][9][10][11] have been proposed as efficient structures for omnidirectional absorption of electromagnetic and acoustic energies, respectively. The name of ABH was first employed by Krylov and Tilman [4] to represent the behavior of flexural waves propagating in a sharp edge that become trapped as they approach the tip.…”

“…On similar backgrounds, Elliot et al [10] employed a porous material together with a metamaterial matching layer as absorbing core. However, Gu and coworkers [11] used angularly distributed fins as the external shell in charge of focusing the acoustic energy towards the absorbing core. Unfortunately, the experimental works didn't present any convincing theoretical analysis supporting the absorbing features measured in their respective characterizations.…”

Dual frequency sound absorption with an array of shunt loudspeakers

“…Traditional absorbers usually require large back cavity or thick depth for low frequency sound absorption [1][2][3][4][5] . Acoustic metamaterials have been studied intensively due to their subwavelength size [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . For example, thickness of metamaterial absorbers can be significantly reduced with space coiling or folding [6][7][8][9] ; however, the absorption performance is hard to be tuned after they are manufactured 8,10 .…”

Theoretical requirements for broadband perfect absorption of acoustic waves by ultra-thin elastic meta-films

“…In the picture of coherent perfect absorption, perfect absorption of acoustic waves has been theoretically proved 29 30 . Other designs to enhance acoustic absorption include porous lamella-crystals 31 , metamaterial absorbers 32 33 34 35 , acoustic black holes 36 37 38 39 40 41 , etc. However, despite of so many designs, the theoretical requirements for broadband perfect absorption with a thin film has not been clearly addressed yet.…”