Asymptotic time domain analysis of sound propagation in a deep ocean sound channel

Abstract

AbstractThis study relates to the time‐domain analysis of sound‐wave propagation in the deep‐ocean sound channel SOFAR (sound fixing and ranging) in the case of a sound source located on or near the channel axis. For asymptotic analysis of response waveforms in the case of an observation point located outside the boundary layer, we used the acoustic ray solution in frequency domain obtained by the acoustic ray tracing method, and derived the acoustic ray expression in time domain. In the case of an observation point located within the boundary layer sound propagation phenomena were clarified that were hard to analyze in terms of the acoustic ray theory. For asymptotic analysis of response waveforms in this case, we proposed a hybrid acoustic ray‐mode expression obtained by combining an acoustic ray with an adiabatic mode. Effectiveness of the proposed asymptotic expression was confirmed by substituting numbers in the acoustic field expressions and completing numerical computations to obtain response waveforms. the results were compared to the reference solutions based on the normal mode theory. It was also demonstrated that numerical computations based on asymptotic expressions are much faster than those based on the normal mode theory. In addition it was found that acoustic field analysis in time domain is more effective than frequency‐domain analysis in terms of physical interpretation of sound wave propagation, since each pulse wave is observed separately.