A Review of Tunable Acoustic Metamaterials

Abstract

Acoustic metamaterial science is an emerging field at the frontier of modern acoustics. It provides a prominent platform for acoustic wave control in subwavelength-sized metadevices or metasystems. However, most of the metamaterials can only work in a narrow frequency band once fabricated, which limits the practical application of acoustic metamaterials. This paper highlights some recent progress in tunable acoustic metamaterials based on various modulation techniques. Acoustic metamaterials have been designed to control the attenuation of acoustic waves, invisibility cloaking, and acoustic wavefront engineering, such as focusing via manipulating the acoustic impedance of metamaterials. The reviewed techniques are promising in extending the novel acoustics response into wider frequency bands, in that tunable acoustic metamaterials may be exploited for unusual applications compared to conventional acoustic devices.

Omindirectional Non-Reciprocity via 2D Modulated Radial Sonic Crystals

“…Examples of metamaterials exhibiting equivalent tensorial densities are numerous and have been used extensively in the literature regarding metamaterials for controlling sound waves, for example in the context of transformation acoustics and cloaking ( [27][28][29][30]). For what concerns active modulation of the equivalent properties, interesting studies have also been reported [31] both theoretically and experimentally [32][33][34][35]. A way of implementing anisotropy in a modulated acoustic medium has also been recently introduced by Allam et al [36].…”

Development of 3D boundary element method for the simulation of acoustic metamaterials/metasurfaces in mean flow for aerospace applications

“…For the last 10 years, the new concepts of acoustic metamaterials, and maetasurfaces have dominated the field of acoustics due to their ability to manipulate acoustic waves as never before and reviewed elsewhere. 2,3,33,34 Periodicity-enhanced metamaterials and metasurfaces are artificial structures with acoustic properties not found in nature and have already been proven in room acoustics 34 and in traffic noise attenuation 2 but they have not been explored for aeronautical applications. 3 Due to the advancement in 3D printing and the capability of making complex structures, there is an increased demand for studying the behaviour of sound propagation for new applications.…”

On the Frequency Up-Conversion Mechanism in Metamaterials-Inspired Vibro-Impact Structures

“…Analytical, numerical and experimental investigations on negative effective mass [16][17][18], double negativity [19], tunable absorption in and transmission through membrane-type acoustic metamaterials [20][21][22][23][24][25][26][27][28], broadband noise mitigation using metamaterial panels with stacked membranes [29], impedance mismatch-driven reduction in transmitted sound energy for structures with attached gas layers [30], acoustic barriers utilizing cellular [31] and flexible [32,33] sub-structures, coupled membranes displaying monopolar and dipolar resonances [34], absorption using degenerate resonators [35], and targeted energy transfer from an acoustic medium to a nonlinear membrane [36] as well as for seismic mitigation [37] have been reported. There have been several studies ranging from tunable structural-scale AM [38,39] to active AM designs [40] that have clearly demonstrated their unique advantages. Utilizing AM to develop practical solutions for low-frequency acoustic noise mitigation is seen to be an area of emphasis.…”