Broadband high sound absorption from labyrinthine metasurfaces

Abstract

Metamaterials are artificial structures which exhibit fascinating properties unreachable by traditional materials. Here, we report on the design, fabrication, and characterization of acoustic metasurfaces consisting of dead-end channels coiled in a 2D plane. It is found that when the area of the channel’s cross section is about 1/10 of the area (4.3 cm × 4.3 cm) of the upper surface of the building block, the sound loss in channels approaches to a critical value, resulting in near-perfect absorption (A > 99%) at resonant frequency. When the building block contains ten channels with specially designed lengths, sound waves can be highly absorbed above a cutoff frequency fc (A > 90% for fc < f < 3fc). The wavelength at the cutoff frequency can be 7.1 times of the thickness of the metasurface. Our results could find applications in noise reduction and sound detection.

Recent progress in acoustic metamaterials and active piezoelectric acoustic metamaterials - A review

“…Anomalous phenomena such as beam-steering (Figure 4(a)) and conversion of propagating waves to evanescent surface waves (Figure 4(b)) were observed using a tapered labyrinthine acoustic metasurface [52,97]. Numerous studies have shown superior performance in space coiling acoustic metasurfaces for real-world applications, including simultaneous modulation of phase shifts and amplitudes of transmitted waves [98], manipulation of sound radiation patterns (Figure 4(c)) [93], one-way acoustic wave propagation (Figure 4(d)) [94], three-dimensional acoustic focusing (Figure 4(e)) [95], acoustic vortex generation (Figure 4(f)) [53], acoustic focusing with high transmission efficiency and ultra-broadband frequency range [99,100], broadband high sound absorption [104], and cloaking [105]. Space coiling structures provide a new way to manipulate acoustic waves by steering spatial phase shift gradients.…”

Ultra-broadband acoustic ventilation barrier based on multi-cavity resonators

“…Sound reduction has always attracted a great deal of attention due to its practical applications in the fields of noise control, environmental protection and architectural acoustics. Recent development of acoustic metamaterials [1][2][3][4][5][6][7][8][9] and metasurfaces [10][11][12][13][14][15][16][17] provides alternative methods for designing various sound insulation and sound absorption systems based on different types of unit cells, such as Helmholtz resonators, [18][19][20][21][22][23][24] coiled Fabry-Perot resonators, [25][26][27] sound membranes, [28][29][30][31] metasurface-based structures, [32][33][34][35][36][37][38][39][40] and split-ring-resonators. [41,42] Generally, these systems have the advantages of high-performance sound insulation and absorption.…”

Theoretical requirements and inverse design for broadband perfect absorption of low-frequency waterborne sound by ultrathin metasurface

“…For more than one decade, the rapid expansion of acoustic metamaterials and metasurfaces has paved a way to manipulate the acoustic wave in unprecedented ways such as negative refraction 7–9 , subwavelength imaging 10,11 , cloaking 12,13 , and one-way transmission 14,15 . Metasurfaces are generally thin structures having subwavelength thickness consisting of unit cells that could give rise to numerous intriguing phenomena 16,17 . With an emphasis on their planarity and ultrathin thickness, metasurfaces are also claimed by some researchers as the planarized version of metamaterials, because both exhibit unusual properties 18,19 .…”

“…With an emphasis on their planarity and ultrathin thickness, metasurfaces are also claimed by some researchers as the planarized version of metamaterials, because both exhibit unusual properties 18,19 . One important category of acoustic metasurfaces is the absorptive metasurface 17,19–45 , which exhibits super absorption for incident waves within a deep subwavelength thickness. Over the past few years, a host of absorptive metasurfaces have been proposed such as membrane-type resonators 20–23 , coiled-up Helmholtz resonators and Fabry-Pérot channels 17,24–32 , coherent perfect absorbers 33,34 and metaporous materials 35–37 .…”