Abstract:

The ideal measurement tool to measure the three-dimensional arrival structure of the noise field is a high-resolution volumetric array sonar system. Unfortunately, such a system is not generally available. However, towed horizontal line arrays are available and can be used, even though they are far from ideal. The beam patterns of a line array are conically symmetric about the axis of the array. When the axis of a horizontal line array is tilted slightly from the horizontal, the vertical character of the beam cones can be used to discriminate between various vertical arrival angles. By combining this character with measurements made on several different towed array headings, an estimate of the three-dimensional directionality of the noise field can be obtained. An algorithm that uses such a technique on single and multiline towed array data to generate an estimate of the three-dimensional directionality of the noise field is described herein. Some results using measured data from a recent noise measurement exercise using a single-towed line array are presented and discussed. [Work supported by ONR and NRL.]