Measurement of the acoustic radiation force on a sphere embedded in a soft solid

TL;DR

This study measures the acoustic radiation force on a sphere in a soft solid, revealing quadratic dependence on acoustic amplitude and highlighting the influence of acoustic Fabry-Pérot effects, with implications for modeling dissipative phenomena.

Contribution

It provides the first quantitative measurement of radiation force on a sphere in a soft solid and introduces a model accounting for Fabry-Pérot effects to relate force and pressure.

Findings

Radiation force evolves quadratically with acoustic amplitude

Strong pressure oscillations due to Fabry-Pérot effect observed

Discrepancies suggest dissipation must be included in models

Abstract

The acoustic radiation force exerted on a small sphere located at the focus of an ultrasonic beam is measured in a soft gel. It is proved to evolve quadratically with the local amplitude of the acoustic field. Strong oscillations of the local pressure are observed and attributed to an acoustic Fabry-P{\'e}rot effect between the ultrasonic emitter and the sphere. Taking this effect into account with a simple model, a quantitative link between the radiation force and the acoustic pressure is proposed and compared to theoretical predictions in the absence of dissipation. The discrepancy between experiment and theory suggests that dissipative effects should be taken into account for fully modeling the observations.