Acoustic Propagation, Internal Waves and Finestructure

We have progressed in our understanding of wave propagation in random media to the point where theoretical predictions of the uctuations in sound waves that have passed through a medium with a known autocorrelation function are quite accurate.This paper is a brief review of that progress in the context of ocean acoustic scattering.Analytic predictions from 4"I moment theory of the range-depth-time phase and intensity uctuations are shown to agree well with measurements of the complex amplitude of sound waves that have propagated through ocean ' regions where the index of refraction statistics are well known.The emphasis is onthe requirement to understand fully the statistics of the ocean medium.Models of the acoustic index of refraction correlations that result from oceanic tides, internal waves, and nestructure processes will be discussed.Comparison of measured and predicted acoustic uctuations will be presented to indicate the level of our understanding.Our knowledge of the scattering processes allows us to consider the problem in an inverse sense.That is, we use the equations of scattering to obtain a stochastic inverse from acoustic data.Examples will be given from the Mid Ocean Acoustic Transmission Experiment, MATE, of both the forward problem and the inverse problem.Models of the oceanic internal wave, nestructure and tidal processes obtained from the measured acoustic uctuations, are compared with those measured.A discussion of the future expectations from stochastic inverse analysis will be given.