The effects of surface variability on received signal statistics.

Abstract

Acoustic propagation through the ocean can result in significant variability in the received signal. The degree of variability depends on the signal frequency and source-receiver range as well as medium variability along the propagation path. Our overall research goal is to develop the capability to classify passive sonar signals using the statistics of the received signal, and to support this goal, we require the capability to simulate statistically-valid signals. When the propagation path interacts with a rough ocean surface, the received signal will vary with time. We have employed the rough surface RAM parabolic wave equation code (Rosenberg, J. Acoust. Soc. Am. 105, 1999) to predict the statistics of low-frequency received signals that interact with the surface (such as in a shallow ocean channel) in order to calculate the effects of the time-varying rough surface scattering on frequency and amplitude statistics. Using a temporally-evolving rough surface, frequency and amplitude statistics are calculated for several ranges and depths. Received signal parameter statistics are compared with published analytical and empirical models. [Work sponsored by ONR Undersea Signal Processing.]