Liquid foam and sound*

How does an acoustic wave dissipate when it propagates through a collection of thin liquid films loaded by the surrounding air and a massive liquid skeleton ?
Liquid foams are complex gas-liquid systems ubiquitous in industrial, food, geophysical context… A liquid foam contains a low liquid fraction (<30%). Its rigidity is due to a liquid skeleton, containing the most important part of the liquid fraction and linked by thin liquid films. The bubble size distribution is strongly polydisperse.
These last years we showed,  over a large frequency range, how a liquid foam was behaving when insonified¹. We showed that liquid foams act as natural and 3D isotropic acoustic metamaterials. Moreover, this work confirmed that liquid foams have important soundproofing properties^1,2.
Recently, we have pushed forward our investigations on the origin of acoustic attenuation in liquid foams and we have revealed that losses are due to both thermal and viscous losses³.

1. J. Pierre, B. Dollet, V. Leroy, PRL 112, 148307 (2014).
2. M. Monloubou, A. Saint-Jalmes, B. Dollet, I. Cantat, EPL, 112(3), 34001 (2015)
3. J. Pierre, C. Gaulon, C. Derec, F.Elias, V. Leroy, EPJE 40, 73 (2017)