Subwavelength perfect acoustic absorption in membrane-type metamaterials: a geometric perspective

Abstract

-Perfect absorption of low frequency sound with subwavelength absorbers has always been a challenge, owing to the difficulty in achieving impedance matching and the inherent weak absorption coefficients of materials at low frequencies. Recently it was shown that when a membrane-type resonator's modes are hybridized through the addition of a thin air-sealed cell with a back reflecting surface, perfect absorption of low frequency acoustic wave can be achieved at a particular tunable frequency. Here we use a geometric perspective, based on the fact that the membrane is very thin and therefore the displacements on both sides of the membrane must be the same, to gain a unified framework for deriving absorption upper bounds as well as for understanding the hybrid resonance and the coherent perfect absorption on the same footing. The latter is another scheme for perfect absorption based on the phase coherence of two counter-propagating waves incident upon the membrane-type resonator. Experiments were carried out to verify some relations predicted by the general framework based on this geometric perspective. Excellent agreement between theory and experiment is seen.

Frequency-doubling effect in acoustic reflection by a nonlinear, architected rotating-square metasurface

“…Acoustic metamaterials composed of local resonators have proven to be of great interest, due to their ability to perform a variety of wave control functionalities at wavelengths much longer than the dimensions of the resonant elements. A wide array of novel acoustic phenomena such as slow sound [1][2][3], negative refraction [4][5][6][7][8][9][10], subwavelength wave guiding [11,12], sound absorption [13][14][15][16][17][18][19][20] and cloaking [21][22][23][24] have been demonstrated in appropriately designed metamaterials. Compared to the metamaterials composed of linear resonators, nonlinear metamaterials offer a rich and diverse set of nontrivial acoustic phenomena, including asymmetric transmission [11,[25][26][27][28], nonlinear pulse and soliton propagation [29][30][31], harmonic generation [32,33] and breathers [34,35].…”

Acoustic and elastic wave propagation in microstructured media with interfaces: homogenization, simulation and optimization

“…1.2. Homogenization waves to surface waves, beam-steering and effective negative refraction; perfect absorption can be reached thanks to a membrane in the unit cell (Ma et al, 2014;Yang, Ma, Yang, & Sheng, 2015). Sound absorption can also be maximized thanks to an array of resonators (Schwan et al, 2017) or of porous layers of resonant inclusions (Lagarrigue, Groby, Tournat, Dazel, & Umnova, 2013).…”

Breaking the barriers: advances in acoustic functional materials

“…Therefore, all the energy from both the original and control waves can couple to the absorber and be completely dissipated if the critical coupling condition is satisfied [179]. Such acoustic CPA has been theoretically predicted and numerically demonstrated by Wei et al [180] and Yang et al [181] and experimentally realized by Meng et al [182]. Song et al extended the acoustic CPA concept into the 2D scenario with higherorder symmetries such as quadrupole and octupole resonances [183].…”