The ability to tune the performance of acoustic metamaterials without structural modifications or complex active control circuits is a remarkable challenge. In this work, we present a square piezoelectric side-branch (PSB) pipe-type structure that consists of the piezoelectric composite sheets (PCSs) on its sidewall and propose the corresponding equivalent electroacoustic circuit model. Compared with the traditional side-branch, theoretical and numerical results show that the thickness of the PSB can be up to $\lambda /200$, and the tunable phase shift of the transmitted wave in the PSB pipe can achieve nearly $2\pi$ by adjusting the capacitances that are connected to the PCSs. The experiment for a square pipe with one PCS is also given to prove the phase control ability of the PSB model. Furthermore, we show that by merely adjusting the external capacitances of the PCSs, switching the functions between the 45° extraordinary transmission and the acoustic focusing for the same incident wave can be exactly realized. Our work provides a promising potential in active controls and integration designs of acoustic metamaterials and devices.

中文翻译：

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基于压电复合侧支的可调谐管式声学超材料

在不进行结构修改或复杂的有源控制电路的情况下，调节声学超材料性能的能力是一项巨大的挑战。在这项工作中，我们提出了一种方形压电侧支（PSB）管型结构，该结构由侧壁上的压电复合板（PCS）组成，并提出了相应的等效电声电路模型。与传统的侧支相比，理论和数值结果表明，PSB的厚度可以达到$\lambda /200$，并且PSB管道中传输波的可调相移几乎可以实现 $\mathrm{2个}\pi$通过调整连接到PCS的电容。还进行了带有一个PCS的方管的实验，以证明PSB模型的相位控制能力。此外，我们表明，仅通过调整PCS的外部电容，就可以准确地在相同入射波的45°超常传输和声聚焦之间切换功能。我们的工作为声学超材料和设备的主动控制和集成设计提供了广阔的前景。