Ambient Noise Effects in the Modeling of Detection by a Field of Sensors.

摘要

This report describes a mathematical model for the ambient noise in the ocean caused by merchant ships. This kind of noise dominates in a frequency range in which many initial detections are made by modern sonar equipment and hence an understanding of it is of considerable interest. A stochastic model for ambient noise is defined and its main properties are explored. The ambient noise process is a function both of time and of space, and it is shown to be a stationary stochastic process as a function of either of these variables. Its characteristic function is calculated as are its first two moments. It is shown that the ambient noise process as a function of time has approximately an exponential autocovariance function and it may be satisfactorily modeled as a Gauss-Markov process. Further, it is shown that the correlation between the ambient noise at two points depends to a good approximation only on the propagation loss function and on the distance between these two points (and not materially on the density or loudness of the noise field). Finally, an effective and practical method for modeling the multidimensional detection process is presented. (Author)