Conventional sound barriers impede airflow at the same time. Recent advances in acoustic metasurfaces provide a solution for air-permeable barriers utilizing the Fano-like interference. While the mechanism of Fano-like interference implies that such a realized device serves a narrow working frequency range around every destructive-interference frequency. Considering the fact that noise usually covers a wide frequency range, designing a broadband acoustic barrier is still a challenge. Here, we theoretically design a planar-profile and subwavelength-thickness ($\sim \lambda /8$) acoustic ventilation barrier prohibitive for sound in a broad range. Our design is a metasurface consisting of a central hollow orifice and two surrounding helical pathways with varying pitch. Thanks to the horn-like helical pathways, the response strength from the monopolar and dipolar modes of the system keeps almost balance in the frequency range of interest, leading to an effective blocking of more than $90\%$ of incident energy in the range of $900-1418$ Hz. Experiments are conducted to validate the proposed design, whose results are consistent with the analytical predictions and simulations. The underlying working mechanism ensures the metasurface capable of handling broadband sound coming from various directions. Our design has the potential in air-permeable yet sound-proofing applications such as simultaneously natural ventilation and noise reduction in green buildings.

中文翻译：

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宽带声学通风屏障

传统的声屏障会同时阻碍气流。声学超表面的最新进展为利用Fano类干扰的透气屏障提供了解决方案。尽管类似Fano的干扰机制暗示了这样一种实现的设备在每个破坏性干扰频率附近都提供了一个狭窄的工作频率范围。考虑到噪声通常会覆盖很宽的频率范围，因此设计宽带声屏障仍然是一个挑战。在这里，我们从理论上设计出平面轮廓和亚波长厚度（$〜\lambda /8$）声屏障阻碍了声音的广泛传播。我们的设计是由中央空心孔口和两个围绕不同螺距的螺旋形路径组成的超表面。得益于像喇叭一样的螺旋形路径，系统的单极和双极模式的响应强度在感兴趣的频率范围内几乎保持平衡，从而有效地阻止了超过$90％$ 的入射能量在 $900-1418$赫兹。进行实验以验证所提出的设计，其结果与分析预测和模拟一致。基本的工作机制确保超颖表面能够处理来自各个方向的宽带声音。我们的设计在透气但隔音的应用中具有潜力，例如在绿色建筑中同时进行自然通风和降噪。