ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

3aUW12. Saturated ocean acoustic intensity statistics as a function of temporal coherence and measurement time.

Nicholas C. Makris

Naval Res. Lab., Washington, DC 20375

Coherence theory is used to analyze the statistics of saturated ocean acoustic intensity measurements. The circular complex Gaussian random field assumption has been used to describe saturated multipath propagation in the ocean for many years. However, previous analysis of intensity statistics in the saturated region have implicity been limited to certain special cases for which the time-bandwidth product of the field measured from a given source is unity. In this paper, the intensity statistics in the saturated region are extended and generalized to be a function of measurement time and temporal coherence. As a result, the well-known 5.6-dB transmission loss (TL) standard deviation of Dyer is found to be a special case of a more general TL standard deviation that approximates 4.34[radical 1/(mu)[radical dB when the time-bandwidth product or number of independent samples (mu) of the intensity average is large. Therefore, the TL standard deviation is shown to approach zero when the time-bandwidth product becomes large, as it must in this deterministic limit. A similar generalization is obtained for the TL mean. Additionally, asymptotic analysis shows that the log-normal distribution for intensity can provide an excellent approximation to TL statistics, contrary to previous contentions.