Generation of Sound Bullets with a Nonlinear Acoustic Lens

TL;DR

This paper introduces a tunable nonlinear acoustic lens made of granular chains that can generate high-energy sound bullets with controllable properties, surpassing linear limitations for applications like biomedical surgery.

Contribution

The study presents a novel nonlinear acoustic lens design that enables controlled generation of high-energy acoustic pulses, supported by theory, simulations, and experimental validation.

Findings

Dramatic focusing effect observed with the nonlinear lens

Ability to control sound bullet properties via static pre-compression

Experimental validation with photoelasticity measurements

Abstract

Acoustic lenses are employed in a variety of applications, from biomedical imaging and surgery, to defense systems, but their performance is limited by their linear operational envelope and complexity. Here we show a dramatic focusing effect and the generation of large amplitude, compact acoustic pulses (sound bullets) in solid and fluid media, enabled by a tunable, highly nonlinear acoustic lens. The lens consists of ordered arrays of granular chains. The amplitude, size and location of the sound bullets can be controlled by varying static pre-compression on the chains. We support our findings with theory, numerical simulations, and corroborate the results experimentally with photoelasticity measurements. Our nonlinear lens makes possible a qualitatively new way of generating high-energy acoustic pulses, enabling, for example, surgical control of acoustic energy.