An acoustic metasurface (AMS) is proposed comprising a panel containing a micro slit of variable depth coupled to a thin cavity of symmetrical coiled spaces. Theoretical and numerical analyses are used to demonstrate that this metasurface has an effective low frequency sound absorption capability (i.e., between 100 Hz and 600 Hz) with a deep-subwavelength thickness. The mechanism underlying the sound absorption is explored by the different ways in which energy is dissipated in the absorber. It was observed that the dissipation of viscous energy takes place in the narrow region of the micro slit and represents 99.7% of the total energy dissipated while the thermal dissipation is 0.3% and occurs in the inner coiled spaces. Furthermore sound absorption of the AMS was investigated experimentally in an impedance tube for normal incidence. The results of the experimental work show that, by varying the depth of micro slit simultaneously with increasing the number of symmetrical coiled spaces, the peak frequency of the absorption can be shifted to a lower frequency without changing the total absorber thickness. A control of 93% of the sound energy, with a relative bandwidth of 50.4% in the frequency range of interest, was acquired with the proposed absorber presenting a thickness of $\lambda /48$. Furthermore, a coupled system was also evaluated experimentally which revealed the broadband absorption to be consistent with the theoretical model.

提出了一种声学超表面 (AMS)，它包括一个面板，该面板包含一个与对称盘绕空间的薄腔耦合的可变深度的微缝隙。理论和数值分析用于证明该超表面具有有效的低频吸声能力（即，在 100 Hz 和 600 Hz 之间）和深亚波长厚度。通过吸收体中能量消散的不同方式来探索吸声的潜在机制。据观察，粘性能量的耗散发生在微缝隙的狭窄区域，占总耗散能量的 99.7%，而热耗散为 0.3%，发生在内部盘绕空间。此外，在垂直入射的阻抗管中通过实验研究了 AMS 的吸声。实验结果表明，通过在增加对称盘绕空间数量的同时改变微狭缝的深度，吸收的峰值频率可以转移到较低的频率而不改变吸收体的总厚度。93% 的声能控制，在感兴趣的频率范围内具有 50.4% 的相对带宽，是通过建议的吸声器获得的，其厚度为$\lambda /48$. 此外，还通过实验评估了耦合系统，这表明宽带吸收与理论模型一致。