Subwavelength broadband sound absorber based on a composite metasurface

Abstract

Suppressing broadband low-frequency sound has great scientific and engineering significance. However, normal porous acoustic materials backed by a rigid wall cannot really play its deserved role on low-frequency sound absorption. Here, we demonstrate that an ultrathin sponge coating can achieve high-efficiency absorptions if backed by a metasurface with moderate surface impedance. Such a metasurface is constructed in a wide frequency range by integrating three types of coiled space resonators. By coupling an ultrathin sponge coating with the designed metasurface, a deepsubwavelength broadband absorber with high absorptivity (>80%) exceeding one octave from 185 Hz to 385 Hz (with wavelength from 17.7 to 8.5 times of thickness of the absorber) has been demonstrated theoretically and experimentally. The construction mechanism is analyzed via coupled mode theory. The study provides a practical way in constructing broadband low-frequency sound absorber.

Review of Broadband Metamaterial Absorbers: From Principles, Design Strategies, and Tunable Properties to Functional Applications

“…Moreover, a subwavelength BMA based on an ultrathin sponge with a composite element surface coating was given experimentally, [ 549 ] which could achieve greater than 80% absorption at 185–385 Hz by controlling the coupling between the sponge coating and the composite element surface. This study can provide a meaningful approach to building broadband low‐frequency absorbers.…”

“…This section focuses on some of the most extensive applications of BMAs, namely, energy harvesting, [72,525] photodetectors, [526][527][528][529][530][531][532][533][534][535] radar-IR dual stealth, [536][537] and bolometers. [538][539][540][541][542][543][544][545][546] Some other essential applications are also presented, including broadband manipulation of mechanical resonance, [547] noise absorbing, [548][549][550][551] imaging, [35,36,[552][553][554] and fabric wearable. [555][556][557][558][559][560] By systematically summarizing the applications of BMAs, the reader can quickly grasp the current hot spots of BMAs application research and simultaneously improve on the shortcomings and further broaden the application scopes of BMAs.…”

“…Apart from the above-mentioned popular applications based on BMAs, there are also some other critical applications, such as mechanical resonance, [547] noise absorbing, [548][549][550][551] imaging, [35,36,[552][553][554] fabric wearable, [555][556][557][558][559][560] etc. We would like to discuss these applications in this section briefly.…”

Perfect Broadband Sound Absorption on a Graphene-Decorated Porous System with Dual-3D Structures

“…Most previous studies of potent sound-absorbing materials dealing with a high-efficiency broadband, a perfect absorber, and low-frequency sound absorption have involved a variety of structures, including granular, foam, , cell-like, − and thin-film layers . Moreover, attempts to use resonant structures have also been reported, such as a micro-perforated panel, coiling up space, , and metasurfaces. , Recently, varied macroscopic resonators with novel preparation methods like three-dimensional (3D) printing have been reported. , Furthermore, foams composed with these resonators have been fabricated for enhanced broadband absorption. − …”

“…17 Moreover, attempts to use resonant structures have also been reported, such as a micro-perforated panel, 18 coiling up space, 19,20 and metasurfaces. 21,22 Recently, varied macroscopic resonators with novel preparation methods like three-dimensional (3D) printing have been reported. 23,24 Furthermore, foams composed with these resonators have been fabricated for enhanced broadband absorption.…”