  In this report we obtain higher order asymptotic expansions of solutions to
wave equations with frictional and viscoelastic damping terms. Although the
diffusion phenomena are dominant, differences between the solutions we deal
with and those of heat equations can be seen by comparing the second order
expansions of them. In order to analyze such effects we consider the weighted
L1 initial data. We also give some lower bounds which show the optimality of
obtained expansions.
