Sonar Array Response to Ambient Noise Directional Fields, Comparing Numerical Results to Closed-Form Estimates

Several studies have been directed towards the development of both numerical and analytical expressions of ambient noise directionality. In this paper, the results of a simplified ambient noise model are employed to examine the response of sonar arrays to directional noise fields. Expressions are found for the array gain against a combination of distant shipping and wind noise employing vertical and horizontal line arrays as examples. The results are compared in each case with array gain against isotropic noise (i.e., directivity index). Array response is found as a function of array orientation, frequency (or size), and steering angle. For the broadside steered line array, a simplified beam response pattern is used to find array gain for these simple analytical noise models. Results compare very well with array gains computed using more precise models of the ambient noise field and exact array response patterns. The implications on sonar design and performance studies are discussed, as well as similar estimates for the response of more complex array configurations. [Study supported by NAVSHIPS, PMS 302–44.]