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Updated: Aug 27, 2025

Author Spotlight: A Stable Phantom Material for Optical and Acoustic Imaging
Published on: June 16, 2023
Omnidirectional acoustic cloaking against airborne sound realized by a locally resonant sonic material
Kei Matsushima1, Yuki Noguchi2, Takayuki Yamada2
1Department of Mechanical Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, 113-8656, Japan. matsushima@mech.t.u-tokyo.ac.jp.
Abstract:
We report that a locally resonant sonic material realizes omnidirectional acoustic invisibility in air. To achieve acoustic cloaking in the low-frequency regime, we axisymmetrically placed elastic rods comprised of silicone rubber and lead around a cloaked object. The radii of the rods are designed to minimize their total scattering cross section for a given frequency. The optimization is performed using an algorithm incorporating multiple scattering theory and gradient-based nonlinear programming. We numerically confirmed that the designed cloaking device suppressed the scattering cross section by almost 92% for all incident directions at the target frequency.
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