No abstract

This paper reports on part of a general investigation that has been carried out to determine the feasibility and limits of performance of high-data-rate underwater digital data communication. Specifically, the paper deals with the amplitude fluctuations that are encountered when high-frequency 0.8-msec duration pulses are transmitted under short-range shallow-water conditions. In the paper, the results of an analysis of experimentally measured amplitude fluctuations are presented. The results, which are presented in the form of amplitude-frequency spectra, autocorrelation functions, and probability density functions, are interpreted in terms of the prevailing climatic conditions, and the results are related to existing relevant theories of fluctuations. Subject Classification: 30.20.

No abstract

In the interference region of forward scattered sound by thermal inhomogeneities, there appears to exist a dominant thermal patch size for scattering at a given frequency. Several published results are examined and it is shown that over a decade of frequencies, the dominant (or effective) scattering patch size shows an f-s/2 frequency dependence. It also appears that a minimum patch size of approximately 1 cm is reached and that the frequency selectivity disappears after this value has been reached.