Sound and vision: visualization of music with a soap film

Abstract

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 iridescences in the soap film, swirl, split and merge in time with the music (see the snapshots in figure below). In this article, we analyse the rich physics behind these 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: generation of vortices, 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 the classroom or to a broader audience.

Charging of a single soap bubble

“…Based on colour matching of interference pattern (fringes) it can be estimated that film thickness of bubble top is 500-900 nm in Figure 2.a, and just before bursting (Figure 2.b) is less than 200 nm [4,6]. These are the values typical for soap bubbles [4][5][6]8].…”

“…Due to the phenomenon of gravitational drainage and evaporation, the film thickness changes over time. For these reasons, the bubbles are much thinner on the top than on the bottom [4,5,6].…”

“…In [8] the droplets of diameter from 0.5 to 10 μm were observed. The droplets distribution after bubble bursting is affected by bubble size, its lifetime, surface tension and used soap solution [6].…”

The Acoustics of Liquid Foams

“…Several non-linear effects have been identified in vibrated soap films. (i) A self-adaptation effect of the soap film thickness has been reported by Boudaoud et al [47,69]: due to centrifugal forces, balanced by Marangoni forces, the liquid flows towards the vibration antinodes, which become thicker [47,69]. (ii) The air, set into net motion by the film vibration via an acoustic streaming effect, induces tangential flow of the liquid inside the films, leading to vortex structures in the plane of the film [46,65,69,70].…”

Survey and Co-Design the Urban Landscape. Innovative Digital Path for Perception Analysis and Data-Driven Project

“…Immaterial data are the real theme of virtual modeling, those elements that explain and describe in a different way what is observed (Bianconi and Filippucci, 2017b;Filippucci et al, 2016). The visualization of the intangible data allows to fully understanding the environment or the observed object Gaulon et al, 2017;Remondino et al, 2009). The widely discussed theme of perception (Ancona, 1970;Arnheim, 1965Arnheim, , 1986Bianconi and Filippucci, 2018b;Filippucci, 2013;Gibson, 2014;Gogel and Tietz, 1977;Gregory, 1998;Ramachandran, 1990) thus finds a new life in the field of neuroscience (Pinotti and Lucignani, 2007), which are linked to the logics of neuro-marketing (Berčík et al, 2016;Giraldi et al, 2017;Jordao et al, 2017;Lahmiri, 2018;Oliviera and Giraldi, 2017;Onay, 2016;Sloan, 2015) used also for urban landscape and public space.…”