Characterization of an underwater metamaterial made of aluminum honeycomb panels at low frequencies

This paper presents a method to characterize the effective properties of inertial acoustic metamaterial unit cells for underwater operation. The method is manifested by a fast and reliable parameter retrieval procedure utilizing both numerical simulations and measurements. The effectiveness of the method was proved to be self-consistent by a metamaterial unit cell composed of aluminum honeycomb panels with soft rubber spacers. Simulated results agree well with the measured responses of this metamaterial in a water-filled resonator tube. A sub-unity density ratio and an anisotropic mass density are simultaneously achieved by the metamaterial unit cell, making it useful in implementations of transformation acoustics. The metamaterial, together with the approach for its characterization, are expected to be useful for underwater acoustic devices.

Automated summary

This paper presents a method for characterizing the effective properties of inertial acoustic metamaterial unit cells for underwater operation using numerical simulations and measurements. The method is validated by a metamaterial unit cell composed of aluminum honeycomb panels with soft rubber spacers, showing good agreement between simulated and measured responses. The sub-unity density ratio and anisotropic mass density achieved by the metamaterial unit cell make it useful for transformation acoustics, with potential applications in underwater acoustic devices.