  The phenomenon of Anderson localization of waves in elastic systems is
studied. We analyze this phenomenon in two different set of systems: disordered
linear chains of harmonic oscillators and disordered rods which oscillate with
torsional waves. The first set is analyzed numerically whereas the second one
is studied both experimentally and theoretically. In particular, we discuss the
localization properties of the waves as a function of the frequency. In doing
that we have used the inverse participation ratio, which is related to the
localization length. We find that the normal modes localize exponentially
according to Anderson theory. In the elastic systems, the localization length
decreases with frequency. This behavior is in contrast with what happens in
analogous quantum mechanical systems, for which the localization length grows
with energy. This difference is explained by means of the properties of the re
ection coefficient of a single scatterer in each case.
