  We study linear and nonlinear wave propagation in a dense and cold hadron gas
and also in a cold quark gluon plasma, taking viscosity into account and using
the Navier-Stokes equation. The equation of state of the hadronic phase is
derived from the nonlinear Walecka model in the mean field approximation. The
quark gluon plasma phase is described by the MIT equation of state. We show
that in a hadron gas viscosity strongly damps wave propagation and also hinders
shock wave formation. This marked difference between the two phases may have
phenomenological consequences and lead to new QGP signatures.
