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Understanding 30 Years of Underwater Acoustic Wavefield Statistics Progress

Over the last 30 years, significant advancements have been made in the study of underwater acoustic wavefield statistics. Key features explored include the small time spreads of early arrivals, the intensity distributions for both early and late arrivals, and the energy scattering characteristics. Our findings indicate that the background sound speed profile plays an influential role in wavefield statistics, contradicting traditional assumptions of a passive background. This work is validated by theoretical results and paralleled with AET observations, highlighting the complexity of wave propagation in inhomogeneous media.

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Understanding 30 Years of Underwater Acoustic Wavefield Statistics Progress

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  1. 30 Years of Progress? M. G. Brown, F. J. Beron-Vera, I. Rypina, I. Udovydchenkov

  2. Our simple expressions account for the following features of the AET measurements: • the remarkably small (O(ms)) time spreads of the early arrivals; • the associated (early arrival) near-lognormal peak intensity pdf; • the large time spreads of the late arrivals; • the associated (late arrival) near-exponential intensity pdf; • the vertical scattering of energy.

  3. Comments on theoretical results • ray and modal phase stability are controlled by the same parameter (a = b) • dependence on the stability parameter a (or b) is multiplicative • derivation of these results does not require that the apex approximation be used • these results suggest that wavefield statistics show very little sensitivity to the structure of dc(z,r) (because of the central limit theorem)

  4. Conclusions • Over the past 30 years progress on understanding underwater acoustic wavefield statistics has been severely hampered by inappropriately assuming that the background c(z) plays a passive role in the process. (Intuition based on the homogeneous background problem fails.) • In the inhomogeneous background problem wavefield statistics at long range are controlled by the background c(z) via a (or b); wavefield statistics show remarkably little sensitivity to the details of dc(z,r). • These statements are supported by ray- and mode-based theoretical results and PE simulations. Agreement between theoretical results and the AET observations is good.

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