Abstract: Expressions for the treatment of interfaces penetrating sound waves, which is used in the finite-difference time-domain modeling of underwater acoustics, are derived. The proposed finite-difference boundary condition expands the scope of application of FDTD to scattering problems of objects with a finite acoustic impedance but without tangential stress. Numerical experiments have been carried out for several scattering problems, which give satisfactory field distributions. All the computation results are in good agreement with theoretical solutions.

Key words: finite-difference time-domain (FDTD) method, finite acoustic impedance, sound scattering