Asymptotic analyses of sound fixing and ranging wave propagation in acoustic channel of deep ocean

In this paper, we propose the asymptotic representations for calculating the sound fields in the sound fixing and ranging (SOFAR) channel of a deep ocean. We present an acoustical ray representation obtained directly from the ray tracing technique for calculation of the sound fields in the illuminated region in the SOFAR channel. We also present the diffracted ray representation and the hybrid ray-mode representation to calculate, respectively, the sound fields in the refraction shadow and the boundary layer. Numerical comparisons with the reference solution obtained from the normal-mode theory have confirmed the accuracy and utility of the asymptotic representations for the sound fields. We have clarified that the various asymptotic representations can provide an effective means for predicting sound fields and for understanding the physical phenomena of sound propagation in the SOFAR channel.