Kawashita, Nakazawa, and Soga [3] give a necessary condition
for the uniform energy decay of the dissipative wave equation
whose principal term has constant coefficients. In their proof,
they construct asymptotic solutions for a suitable family
of the Cauchy data. In this paper, instead of the asymptotic
solutions, we consider the semiclassical measure associated
with the family and extend this result to the variable coefficient
case. Moreover we give some lower bound estimate for the energy
decay.