Adaptive membrane-type acoustic metamaterial with autonomous tuning to incident sound fields

膜型声学超材料（MAM）由一个薄的预应力膜与质量连接到膜。尽管这些超材料非常轻和薄，但它们在低频范围内表现出窄频带（所谓的反共振），具有非常高的隔音值-远远高于具有相同质量的均匀壁。这使得MAM成为对噪声控制处理的质量和尺寸有严格限制的噪声控制应用的非常有前途的解决方案。然而，反共振的窄带宽是MAM应用于具有变化的音调频率的噪声源（例如，由旋转机器产生）的相当大的抑制因素。该项目的目标是首次展示一种自适应MAM，该自适应MAM能够自主调谐到具有包含宽带和音调分量的频谱的入射声场。在该项目中，自适应控制算法将与驱动方法和集成在MAM上的传感器一起开发，以实现与被动MAM相比更好的宽带和音调降噪。特别地，自适应MAM将能够识别噪声源频谱中的音调与MAM的反谐振频率之间的偏差，并且它将在毫秒内自适应以使反谐振频率适应该音调。将研究自适应MAM相对于非线性以及MAM的动态特性的变化（例如，由于温度变化）的灵敏度。自适应控制算法将被开发为相对于这些干扰是鲁棒的，从而增强可调MAM的适用性，更实际的噪声控制应用。作为该项目的最终结果，将建立一个可调MAM的实验演示器，并针对不同的噪声源配置进行测试。

Membrane-type acoustic metamaterials (MAM) consist of a thin pre-stressed membrane with masses attached to the membrane. Even though these metamaterials are very lightweight and thin, they exhibit narrow frequency bands (so-called anti-resonances) in the low frequency range with very high sound insulation values - much higher than a homogeneous wall with the same mass. This makes MAM a very promising solution for noise control applications with strict constraints on the mass and size of noise control treatments. The narrow bandwidth of the anti-resonances, however, is a considerable inhibiting factor for the application of MAM to noise sources with changing frequencies of tones (e.g. generated by rotating machines). The objective of this project is to demonstrate for the first time an adaptive MAM which is capable of autonomously tuning itself to an incident sound field with a spectrum containing both broadband and tonal components. In the project, an adaptive control algorithm will be developed in conjunction with actuation methods and sensors integrated on the MAM to achieve improved broadband and tonal noise reduction, compared to the passive MAM. In particular, the adaptive MAM will be capable of identifying deviations between a tone in the noise source spectrum and the anti-resonance frequency of the MAM and it will adapt itself within milliseconds to adapt the anti-resonance frequency to this tone. The sensitivity of the adaptive MAM with respect to non-linearities as well as changes of the dynamic properties of the MAM (e.g. due to temperature changes) will be investigated. The adaptive control algorithm will be developed to be robust with respect to these disturbances, thus enhancing the applicability of the adjustable MAM to more practical noise control applications. As a final result of this project, an experimental demonstrator of an adjustable MAM will be built and tested for different noise source configurations.