Deep subwavelength hybrid metamaterial for low-frequency underwater sound absorption by quasi-Helmholtz resonance

We proposed an acoustic metamaterial with deep subwavelength thickness for low-frequency underwater sound absorption. The hybrid has a perforated facesheet, fluid-filled square honeycomb core inside rubber coating, and fixed backsheet. A theoretical model is established to predict the absorption performance of this based on theory micro-perforated panel electro-acoustic analogy. agrees well our finite element simulation. Results suggest that perfect (99.9%) occurs at 375 Hz, which only 1/80 wavelength. According simulation, most energy consumed by coating. It can be analyzed coating replaces fluid in resonant cavity improving capacitance resistance triggering quasi-Helmholtz resonance. This also exhibits broadband parallel design different perforations, promising potential engineering applications.