Spatial‐Correlation Functions for Various Noise Models

Observations indicate that noise in the ocean is a superposition of an isotropic noise field and an anisotropic noise field originating at the surface. Models which produce such noise fields are described, and the spatial‐correlation functions are obtained. The volume‐noise model, which produces an isotropic noise field, consists of noise sources uniformly distributed within a sphere. A single‐frequency component of each noise source is considered; the mean‐square output of each is the same, the relative phases are random, and inverse spreading occurs. It is shown that for a very large sphere the spatial correlation is the same as that given by Marsh for a homogeneous isotropic noise field and by the Faran and Hills noise model, which consists of noise sources on the surface of a large sphere. The surface‐noise model consists of noise sources uniformly distributed on a large circular area of a plane. The noise sources are assumed to be directional, in addition to having the properties listed above. The spatial correlation is obtained as a function of the directionality of the noise sources, the spacing of the receivers and their orientation with respect to the surface, and the electrical delay.