Acoustic perfect absorbers via spiral metasurfaces with embedded apertures

Abstract

In this work, we analytically and experimentally present perfect acoustic absorbers via spiral metasurfaces composed of coiled channels and embedded apertures. Perfect absorption (reaching 0.999 in experiments) is realized with an ultra-thin thickness down to ∼1/100th of the operating wavelength. Owing to the superior impedance manipulation provided by the embedded apertures, perfect absorption with tunable frequencies is demonstrated. Our results would contribute to paving a way towards designing thin and light absorbers for the low frequency absorption challenge.

The Present and Future Role of Acoustic Metamaterials for Architectural and Urban Noise Mitigations

“…In the past few years, researchers have demonstrated the efficacy of several hybrid metasurface absorbers, combining the traditional perforated plate with subwavelength-sized metastructures. These acoustic absorbers are based on the concept of impedance-matching of surfaces with hybrid resonance [42,43]. When the acoustic impedance of a hybrid metasurface matches with that of the incoming sound wave, the metasurface neither reflects nor transmits the incoming sound wave; it almost perfectly absorbs the incoming sound energy.…”

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“…The phase delay is calculated as ∆∅ = , where is the acoustic wave number and is the effective channel length [13]. Recently, several types of space coiling structures have been demonstrated for low-frequency sound attenuation, such as co-planar spiral tubes [60], axially coupled circular tubes [73], coiled air chambers [74], spiral metasurfaces [75], and labyrinthine structures [76][77][78]. [13], © 2016 Author(s) under a Creative Commons Attribution Non-Commercial License 4.0 (CC BY-NC), and Yang et al [44], © 2015 Académie des sciences, respectively.…”

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