Invisible design and acoustic scattering of metamaterial plates with active feedback control

With the development of active sonar technology, the poor performance of anechoic tiles in avoiding low-frequency detection has emerged. Then tunable mechanical metamaterials with active control systems have extended applications. This work proposes active metamaterial plates composed of two plates and periodic four-link mechanisms with local resonators. By coils and magnets as well as external voltage, active feedback control is used to regulate the dynamic effective density. Based on the Fourier transform and Wiener–Hopf method, a theoretical model is derived to study the scattering of sound waves from active metamaterial plates. The fluid–structure interaction between the acoustic medium and metamaterial plates is considered. Then the vibroacoustic coupling is investigated to achieve the invisible design of submarines. Results show that the scattered sound pressure within a negative density region is effectively reduced with proper acceleration and displacement feedback coefficients. Furthermore, the finite element simulation and acoustic scattering experiment are performed to support the theoretical derivation. This research is expected to provide further insights for improving invisible effects of underwater vehicles.