Sound and Vision: Visualization of music with a soap film, and the physics behind it

C Gaulon (1) , C Derec (1) , T Combriat (2) , P Marmottant (2) , F Elias (3, 1)

1 MSC - Matière et Systèmes Complexes
2 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
3 UPMC - Université Pierre et Marie Curie - Paris 6

A vertical soap film, freely suspended at the end of a tube, is vibrated by a sound wave that propagates in the tube. If the sound wave is a piece of music, the soap film comes alive: colours, due to the soap film iridescences, swirl, split and merge at the rate of the music (see the snapshots on figure 1 below). In this article, we analyse the rich physics behind those fascinating dynamical patterns: it combines the acoustic propagation in a tube, the light interferences, and the static and dynamic properties of soap films. The interaction between the acoustic wave and the liquid membrane results in capillary waves on the soap film, as well as non-linear effects leading to a non-oscillatory flow of liquid in the plane of the film, which induces several spectacular effects: vortices generation, diphasic dynamical patterns inside the film, and swelling of the soap film under certain conditions. Each of these effects is associated with a characteristic time scale, which interacts with the characteristic time of the music play. This article shows the richness of those characteristic times that lead to dynamical patterns. Through its artistic interest, the experiments presented in this article provide a tool for popularizing and demonstrating science in classroom or broader audience.

Domaines: Matière Molle [cond-mat.soft]

C Gaulon, C Derec, T Combriat, P Marmottant, F Elias. Sound and Vision: Visualization of music with a soap film, and the physics behind it. 2017. ⟨hal-01487166⟩