This paper analyses the sound decay in an acoustically treated rectangular space from the view point of wave acoustics. and a new method of calculating complex eigenvalue is given.

The blasting vibration of creep mass slope of Longtan hydropower station is observed, interpreted and analyzed. The experiential formula of decay for the blasting earthquake wave is obtained.

By using the perturbed-energy method, the exponential decay of the solution is obtained for the nonlinear wave equations with time-dependent coefficients and dissipative boundary condition.