Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

Abstract

This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

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

“…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]. Nevertheless, the design of nonlinear metamaterials, which was initially investigated in optics for the purpose of enhancing the higher harmonic generation [36][37][38], has been studied much less extensively in the acoustic field [39].…”

Acoustic cloaking design based on penetration manipulation with combination acoustic metamaterials

“…[1][2][3][4][5] Theoretical analysis, numerical calculation, and experimental test were conducted to analyze the distinctive acoustic phenomenon, such as unidirectional transmission, acoustic filtering, acoustic focusing, acoustic negative refraction, acoustic waveguiding, acoustic collimating, and so on. 6,7 As a kind of artificial inhomogeneous material, acoustic metamaterials are synthetic materials formed by a periodic variation in the mechanical properties of materials (i.e., elasticity modulus and mass density), and it can suppress and manipulate acoustic waves transmission. [8][9][10][11] Acoustic metamaterials have unique mechanical properties, such as negative equivalent mass density, negative equivalent bulk modulus, and negative shear modulus, which are achieved through topology design of micro-structure and materials distribution design.…”