Magnetic fields and acoustic waves are the two fundamental measures to perceive underwater objects, which, however, have never been simultaneously handled before. In this work, we propose and demonstrate a biphysical submillimeter-thick metamaterial coat that can simultaneously make underwater objects invisible to both magnetic fields and acoustic waves. The conformal coat is a subtle integration of an open-cavity acoustic absorber made of a dissipative acoustic metasurface (AMS) and a bilayer magnetic cloak. Experimentally, a magnetic cloaking effect with a field disturbance ratio of <0.5% is obtained over a broad-frequency range (10–250 kHz), and the compound metamaterial coat can strongly attenuate ultrasonic waves with a near-unity absorptivity. The magnetic subcoat can be freely combined with various AMS layers to achieve a wideband acoustic stealth effect for different spectral regimes. This work may open up a new way to build multifunctional devices for various waterborne applications.

磁场和声波是感知水下物体的两个基本措施，但是，以前从未同时对其进行处理。在这项工作中，我们提出并证明了一种双物理的亚毫米厚的超材料涂层，它可以同时使水下物体对磁场和声波均不可见。保形涂层是由耗散声学超表面（AMS）和双层电磁披风制成的敞腔吸声器的精细结合。在实验上，在较宽的频率范围（10–250 kHz）中获得了场干扰比<0.5％的磁掩盖效应，并且复合超材料涂层可以以几乎统一的吸收率强烈衰减超声波。磁性底涂层可以与各种AMS层自由组合，以实现针对不同光谱范围的宽带声隐身效果。这项工作可能会为构建用于各种水性应用的多功能设备开辟新的途径。