Structure and dynamics of fractal aerogels

Silica aerogels form mutually self-similar fractal structures for a broad range of densities and preparation conditions. This allows to scale dynamical results obtained on longitudinal acoustic waves up to the onset of the phonon to fracton crossover. An "effective" value of the fracton dimension {Mathematical expression} is found, and various possible interpretations of that value are discussed. © 1987 Springer-Verlag.