Experimental Realization of a Nonlinear Acoustic Lens with a Tunable Focus

TL;DR

This paper demonstrates a nonlinear acoustic lens using sphere chains that can produce high-amplitude focused sound pulses, with tunable focus controlled by pre-compression, validated through experiments and analytical models.

Contribution

It presents the first experimental realization of a tunable nonlinear acoustic lens using sphere chains supporting solitary waves.

Findings

The lens produces high-amplitude sound bullets with minimal oscillations.

Focal point can be tuned via pre-compression of the chains.

Experimental results match analytical predictions across focus locations.

Abstract

We realize a nonlinear acoustic lens composed of a two-dimensional array of sphere chains interfaced with water. The chains are able to support solitary waves which, when interfaced with a linear medium, transmit compact pulses with minimal oscillations. When focused, the lens is able to produce compact pressure pulses of high amplitude, the "sound bullets". We demonstrate that the focal point can be controlled via pre-compression of the individual chains, as this changes the wave speed within them. The experimental results agree well both spatially and temporally with analytical predictions over a range of focus locations.