  We used coherent light scattering in a multi-speckle detection scheme to
investigate the mesoscale dynamics in aqueous foam. Time-resolved correlation
of the scattered speckle intensities reveals the details of foam dynamics
during aging. We introduce Temporal Contrast Analysis, a novel statistical tool
that can be effective in characterizing structural rearrangements. Using
Temporal Contrast Analysis we were able to detect two distinct dynamical
components present during foam aging: spontaneous and intermittent,
avalanche-like events and continuous, flow-like rearrangements in the foam
structure. We were able to measure these contributions separately from the
intrinsic statistical noise contribution, and thereby independently analyze the
decay of each dynamical component during foam aging process.
