Soap Film Opera: the dance of soap bubbles

Blow continuously on a film of soap: a bubble will swell, detach, fly away and become iridescent in the sunlight. But if the breath oscillates, like that produced by a sound wave, the soap film starts to vibrate like the liquid membrane of a drum. We observed these vibrations by placing a loudspeaker at the end of a tube at the other end of which the soap film is formed. When the loudspeaker plays a piece of music capable of exciting the resonant frequencies of the tube, the dynamic structures that appear on the soap film are fascinating both for their beauty and for the richness of the underlying physics. Depending on the frequency and intensity of the acoustic forcing, capillary waves are observed as well as a rich dynamic in the film: generation of vortices, multiple patches of colour evolving according to astonishing movements… and even regeneration of the film delaying the final burst!

This dynamic is due to the effect of the inertia of the liquid and the air, or to the redistribution of the soap molecules during the vibration, leading to flows in the plane of the film. Each of these effects has its own characteristic time, which interacts with the rhythm of the musical forcing. In this way, different pieces of music lead to different dynamics because of their tessitura, tempo and musical volume.

Several videos of soap films dancing on different music pieces can be watched on my YouTube channel.

Performances

Through their artistic interest, these experiments illustrate numerous physical phenomena in the fields of acoustics, optics, hydrodynamics and soft matter, and thus provide an original tool for scientific mediation and the popularisation of science. With the Artemisia trio (Tania Castro – flute, Ines Lopez – viola, Alessandra Magrini – harp), we have given several Art and Science shows combining music, images and scientific popularisation. Please clic here to see a « Conférence expérimentale » that we showed in december 2023 at the ESPCI.

 

Reference

C. Gaulon, C. Derec, T. Combriat, P. Marmottant et F. Elias, Sound and Vision : Visualization of music with a soap film, European Journal of Physics 38 (2017) 045804

Funded Art & Science projects

Science popularisation