We design an acoustic switch based on a spiral kirigami metasurface using numerical simulations and evaluate its performance experimentally. By etching an Archimedean spiral on a thin aluminum sheet, a band gap in out-of-plane vibration modes can be generated. The band gap is significantly suppressed by axially stretching the kirigami spiral structure, extending sound propagation to a broader frequency range. The kirigami metasurface is easily deformed and manipulated and can switch the energy transmission on and off in the desired operating-frequency range, providing an alternative design strategy for acoustic metasurfaces.

Switching on and off acoustic waves through metamaterials has potential in noise canceling, underwater detection, and communication. However, traditional acoustic designs are challenging in manipulating underwater acoustic waves when the device thickness is less than wavelength. Here we report an alternative design of an underwater metasurface-based acoustic switcher to achieve this goal. The switching mechanism is revealed by combing acoustic diffraction of grating with mode conversion of double-layer PMMA plates. The device is tuned to control wave transmission by changing grating angle. Furthermore, we experimentally fabricate the metasurface acoustic switcher. The broadband-switching performance is realized to control underwater target detection and to produce binary digital encoding for acoustic waves. The proposed metasurface acoustic switcher offers the advantages of broadband performance and thin structure, which promises the opportunity for designing next-generation broadband-switching devices in underwater acoustic detection and communication.

In underwater environments, controlling the propagation of acoustic waves faces complex physical challenges—especially under noisy conditions, variations in seawater density, and large-scale fluctuations in sound speed—that conventional acoustic techniques struggle to address effectively. This paper explores a novel research paradigm for achieving tunable negative refraction underwater. The proposed approach utilizes a metamaterial structure composed of a one-dimensional acoustic grating and a one-dimensional phononic crystal, offering a breakthrough theoretical scheme for tunable negative refraction of sound waves in aquatic settings. The paper begins by outlining the key issues in underwater acoustics research and the limitations of existing technologies, including challenges in underwater acoustic communication, imaging, and detection. It then provides an in-depth analysis of the fundamental structures of one-dimensional acoustic gratings and one-dimensional phononic crystals, detailing the mechanisms by which negative refraction is realized. Finally, the study investigates the tunability of the negative refraction phenomenon as dictated by the structural parameters.

To address the bottleneck of insufficient broadband sound insulation performance of traditional sound insulation materials at the subwavelength scale, this paper designs a composite subwavelength sound insulation unit (size: 20 mm × 20 mm × 5 mm) composed of Ti₃C₂T_x MXene, and PZT-5H piezoelectric ceramics, and porous aluminum alloy. Based on the electromagnetic-structural-acoustic multi-physics field coupling theory, the regulation laws of external electric field intensity and effect of MXene layer number on sound insulation performance are systematically investigated via numerical simulation, and the sound insulation enhancement mechanism dominated by dielectric tunability is clarified. The results show that the dielectric constant of MXene increases monotonically with the external electric field intensity, and the optimal regulation sensitivity is achieved when the layer number N = 3; when the electric field intensity increases from 0 V to 500 V, the equivalent density of the system increases from 1.25 g/cm³ to 1.87 g/cm³, the acoustic impedance increases from 3.42 × 10⁶ Pa·s/m³ to 5.13 × 10⁶ Pa·s/m³, the average transmission loss TL in the 200–600 Hz frequency band is increased by 2 dB compared with the state without electric field, and the sound pressure on the transmission side is reduced by 3.56% at 400 Hz; the vibration displacement of PZT decreases from 0.0055 mm to nearly 0 mm with the increase in electric field, and the electric field energy density increases from 0 J/m³ to 7.47056 × 10³ J/m³, verifying the core mechanism of converting electromagnetic energy into structural damping through dielectric loss. This study supplements parameter sensitivity analysis and literature benchmark comparison to compensate for the lack of experimental data, confirming the stability and rationality of the simulation results. The established cross-field coupling framework of “dielectric regulation–density optimization–impedance matching–sound insulation enhancement” fills the theoretical gap of the coupling mechanism of MXene in the field of subwavelength sound insulation, and provides new theoretical and technical pathways for the design of broadband active sound insulation materials in the 200–1000 Hz frequency range.