A fourth-order energy for the three-dimensional wave equation with second-order absorbing boundary conditions Original Research Article

We introduce a fourth-order energy for the three-dimensional wave equation in rectangular domains with second-order absorbing boundary conditions. A decay rate of the energy in the domain with respect to time is estimated in terms of the boundary integral. Absorbing boundary conditions considered in this paper include the treatment of the case of annihilation of obliquely incident waves arriving at the boundary. Numerical results are also shown.