Analysis of characteristics of underwater sound propagation in the ocean by a finite difference time domain method

Many methods of calculation that are useful in deep water like the Pacific Ocean have recently been reported for obtaining sound propapation characteristics. Thr development of new method is expected for shallow water in this paper, the finite difference time domain (FDTD) method, which takes account of attenuation, is proposed to calculate the propagation of sound in shallow water with a lossy seabed. The benchmark problem proposed by the Acoustical Society of America was solved by the FDTD method and its results were compared with other methods. The contour pattern of the transmission loss in water and in sediment agreed well with the results of an accurate coupled-mode calculation. A series of propagated pulse waveforms in the same model is also calculated. It is useful for us to recognize the sound propagation not only in water but also in sediment. The FDTD method shows the pulse waveforms with interference between direct wave and reflected waves. These. results show the validity of the FDTD method.