Dispersive acoustic metamaterials (AMMs) with graded refractive index is promising in acoustic sensing enhancement by providing acoustic rainbow trapping (ART) effect. However, previous solutions to this type of AMMs are based on 2D unit cells that require infinite or very large size in the third dimension; they cannot integrate with conventional acoustic sensors without deteriorating the ability of acoustic wave manipulation. In order to advance their practical applications, this paper proposes an axisymmetric, microphone embedded AMM device with gradient profile as well as gradient plate thickness and gradient gap width along the axis. Both numerical simulations and experiments are performed to examine the ART effect of the proposed AMM device and demonstrate its excellent capacity of acoustic pressure amplification and multi-band acoustic filtering. Deploying a microphone in the gap does not disturb the acoustic field, so the proposed AMM sensor experimentally achieves remarkable acoustic gains over one order of magnitude. Sound waves of different frequencies are picked up by microphones at different gaps, realizing the real-time spatially splitting of the sound spectrum. The proposed AMM provides excellent immunity to broadband noise and a little weak suppression of the single tone noise while significantly amplifying acoustic signals of a given frequency.

中文翻译：

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一种能够多波段滤波和放大的基于声学超材料的传感器

具有渐变折射率的色散声学超材料 (AMM) 通过提供声学彩虹陷阱 (ART) 效应在声学传感增强方面很有前景。但是，以前针对此类 AMM 的解决方案是基于 2D 晶胞，在三维空间中需要无限或非常大的尺寸；它们无法在不降低声波处理能力的情况下与传统声学传感器集成。为了推进它们的实际应用，本文提出了一种轴对称、麦克风嵌入式 AMM 设备，该 AMM 设备具有梯度轮廓以及沿轴的梯度板厚度和梯度间隙宽度。进行了数值模拟和实验，以检查所提出的 AMM 设备的 ART 效果，并证明其出色的声压放大和多频段声学滤波能力。在间隙中部署麦克风不会干扰声场，因此所提出的 AMM 传感器在实验上实现了超过一个数量级的显着声学增益。不同频率的声波被不同间隙的麦克风拾取，实现声谱的实时空间分割。所提出的 AMM 提供了出色的宽带噪声抗扰性和对单音噪声的轻微抑制，同时显着放大了给定频率的声学信号。因此，所提出的 AMM 传感器在实验上实现了超过一个数量级的显着声学增益。不同频率的声波被不同间隙的麦克风拾取，实现声谱的实时空间分割。所提出的 AMM 提供了出色的宽带噪声抗扰性和对单音噪声的轻微抑制，同时显着放大了给定频率的声学信号。因此，所提出的 AMM 传感器在实验上实现了一个数量级的显着声学增益。不同频率的声波被不同间隙的麦克风拾取，实现声谱的实时空间分割。所提出的 AMM 提供了出色的宽带噪声抗扰性和对单音噪声的轻微抑制，同时显着放大了给定频率的声学信号。