Acoustical characterization of concentrated bubbly media

Bubbles are known to be strongly resonant acoustic scatterers. As such, their presence in a fluid, even for amounts of gas as low as 1%, highly impacts the propagation of acoustic waves. Ultrasounds are, thus, a great tool for bubble distribution measurements in opaque fluids. Additionally, diluted media models have been shown to have a good agreement with experiments at volume fraction below 1%. One of the aims of our study is to determine the limit volume fraction beyond which the models start to fail. To achieve that, we measure relfection and transmission of ultrasounds through bubbly media ranging from 5% to 60 % of gas volume fraction. Samples are polydisperse thin slabs with median radii ranging between 30 and 180 μm. Alongside experimental measurements, numerical simulations are carried out with monodisperse distributions. Up to 10%, we find a good agreement between the independent scattering approximation and our experimental results.