# Ultrasound transmission through monodisperse 2D microfoams

## TL;DR

This study experimentally investigates ultrasound transmission through a controlled monolayer of monodisperse microbubbles, revealing that sound velocity depends on the gas phase and attenuation involves viscous dissipation, advancing understanding of liquid foam acoustics.

## Contribution

It provides new experimental insights into ultrasound propagation in monodisperse microfoam layers, highlighting the roles of gas phase and liquid network structure.

## Key findings

- Sound velocity depends mainly on the gas phase.
- Liquid network structure influences sound transmission.
- Attenuation is primarily due to viscous dissipation in gas pores.

## Abstract

While the acoustic properties of solid foams have been abundantly characterized, sound propagation in liquid foams remains poorly understood. Recent studies have investigated the transmission of ultrasound through three-dimensional polydisperse liquid foams (Pierre et al., 2013, 2014, 2017). However, further progress requires to characterize the acoustic response of better controlled foam structures. In this work, we study experimentally the transmission of ultrasounds through a single layer of monodisperse bubbles generated by microfluidics techniques. In such a material, we show that the sound velocity is only sensitive to the gas phase. Nevertheless, the structure of the liquid network has to be taken into account through a transfer parameter analogous to the one in a layer of porous material. Finally, we observe that the attenuation cannot be explained by thermal dissipation alone, but is compatible with viscous dissipation in the gas pores of the monolayer.