Sound through the internal wave field

We review the subject of sound propagation through the random ocean internal wave field. Among the assumptions that are usually made, two are identified as not always valid: the Markov approximation and the expansion around a deterministic ray. When these approximations are valid, and the internal wave field known, acoustic phase fluctuations are very accurately predicted and intensity fluctuations reasonably well calculated. For the calculations of statistical moments of the acoustic field, the two techniques of moment equations and path integrals have been developed to a high degree, and give similar results. Among all other statistical quantities, the probability density function for intensity has received the most attention, but no satisfactory theory has been developed for this or other quantities. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.