Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore.
School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China.
Sensors (Basel). 2019 Feb 15;19(4):788. doi: 10.3390/s19040788.
Acoustic rainbow trappers, based on frequency selective structures with graded geometries and/or properties, can filter mechanical waves spectrally and spatially to reduce noise and interference in receivers. These structures are especially useful as passive, always-on sensors in applications such as structural health monitoring. For devices that face space and weight constraints, such as microelectromechanical systems (MEMS) transducers and artificial cochleae, the rainbow trapping structures must be compact as well. To address this requirement, we investigated the frequency selection properties of a space-saving design consisting of Helmholtz resonators arranged at sub-wavelength intervals along a cochlear-inspired spiral tube. The height of the Helmholtz resonators was varied gradually, which induced bandgap formation at different frequencies along the length of the spiral tube. Numerical simulations and experimental measurements of acoustic wave propagation through the structure showed that frequencies in the range of 1⁻10 kHz were transmitted to different extents along the spiral tube. These rainbow trapping results were achieved with a footprint that was up to 70 times smaller than the previous structures operating at similar bandwidths, and the channels are 2.5 times of the previous structures operating at similar bandwidths.
基于渐变几何和/或属性的频率选择结构的声学彩虹俘获器，可以对机械波进行光谱和空间滤波，从而降低接收器中的噪声和干扰。这些结构在结构健康监测等应用中作为无源、始终开启的传感器特别有用。对于面临空间和重量限制的设备，例如微机电系统 (MEMS) 换能器和人工耳蜗，彩虹俘获结构也必须紧凑。为了满足这一要求，我们研究了一种节省空间的设计的频率选择特性，该设计由沿耳蜗启发的螺旋管以亚波长间隔排列的亥姆霍兹谐振器组成。亥姆霍兹谐振器的高度逐渐变化，这导致在螺旋管的长度上不同频率形成带隙。通过结构传播声波的数值模拟和实验测量表明，在 1⁻10 kHz 的频率范围内，沿螺旋管以不同程度传输。与在类似带宽下工作的先前结构相比，这些彩虹俘获结果的足迹小了 70 倍以上，而通道则是在类似带宽下工作的先前结构的 2.5 倍。
