Three-dimensional locally-resonant underwater lens for low-frequency sound focusing

Abstract

Broadband underwater sound focusing in the low-frequency range is crucial for a wide array of applications, such as battery-free environmental monitoring and sensing. However, achieving low-frequency underwater focusing typically necessitates bulky, heavy structures that hinder practical deployment. In this work, we present a three-dimensional lens composed of cavity-based locally resonant scatterers, enabling a highly efficient design for manipulating low-frequency waterborne sound through densely packed lattice configuration. We experimentally validate its broadband focusing performance over the 20-35 kHz range.