Abstract
The vibration of a soap film set into motion by a sound wave is studied
experimentally and
theoretically. In contrast with the well separated resonances of a
solid membrane, the modes of a
liquid film exist in wide ranges of frequencies and the vibration amplitude
is large for all forcing
frequencies. This is due to the adaptation of the film mass distribution
which concentrates at the
antinodes as observed by interference fringes in monochromatic light.
The theoretical model takes
into account the variation of surface tension with thickness and explains
the experimental results.