Zero index metamaterials have shown the ability to achieve total transmission or reflection by embedding particular defects with various effective parameters. Here, we present that tunable sound transmission can be realized by configuring a subwavelength-sized dopant inside zero index acoustic metamaterials. Despite its small spatial signature, the dopant is able to strongly interact with the acoustic waves inside the whole zero index metamaterials. It is due to the essence of the zero effective index that can homogenize the pressure field within the metamaterials. Sound transmission can thus be fully switched on and off by adjusting the dopant's surface impedance. A simple rectangular cavity with varied lengths is proposed to provide the required impedance boundary. Our model of correlating the dopant design with sound transmission performance is validated theoretically and numerically. We further demonstrate the utilization of the proposed design to effectively modulate the sound focusing effect. Such a dopant-modulated sound transmission scheme, with its simplicity and capability, has potential applications in fields like noise control and ultrasonography.

中文翻译：

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零折射率声学超材料的掺杂物调制声音传输

零折射率超材料已经显示出通过嵌入具有各种有效参数的特定缺陷来实现总透射或反射的能力。在这里，我们提出可调谐声音的传输可以通过在零折射率声学超材料内部配置亚波长尺寸的掺杂剂来实现。尽管其空间特征很小，但掺杂剂仍能与整个零折射率超材料内部的声波强烈相互作用。由于零有效指数的本质，可以使超材料中的压力场均匀。因此，可以通过调节掺杂剂的表面阻抗来完全打开和关闭声音传输。提出了一种具有不同长度的简单矩形腔，以提供所需的阻抗边界。我们将掺杂剂设计与声音传输性能相关联的模型在理论和数值上得到了验证。我们进一步证明了所提出的设计可以有效地调节声音聚焦效果。这种掺杂剂调制的声音传输方案具有简单性和功能性，在诸如噪声控制和超声检查等领域具有潜在的应用。