Accession Number : ADA330139

Title :   Three-Dimensional Noise Field Directionality Estimation from Single-Line Towed Array Data

Descriptive Note : Journal article

Corporate Author : NAVAL RESEARCH LAB STENNIS SPACE CENTER MS CENTER FOR ENVIRONMENTAL ACOUSTIC S

Personal Author(s) : Wagstaff, Ronald A. ; Newcomb, J.

Report Date : AUG 1997

Pagination or Media Count : 10

Abstract : For many reasons. the three dimensional (3-D) arrival structure at the undersea ambient noise field is at interest to the research and development community. One reason is that the arrival structure can be used to estimate the beam noise at an array, which may be required to estimate the performance at the array as an operational Navy asset or a scientific measurement tool. Another reason is that there are clues inherent in the vertical arrival structure that relate to the nature at the acoustic propagation along the azimuths at the noise sources. Similarly, there are also clues in the horizontal arrival structure of the undersea ambient noise field that relate to the azimuthal distribution at the noise sources. Both at these classes at clues are important in the verification and validation at undersea ambient noise models. The ideal measurement tool to measure the 3-D arrival structure at 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 at a line array are conically symmetric about the axis at the array. When the axis of a horizontal line array is tilted slightly from an elevation angle at 0 deg the vertical character at the beam cones can be used to discriminate between various vertical arrival angles. Combined with measurements made on several different towed array headings, an estimate at the 3-D directionality at the noise field can be obtained. An algorithm that uses such a technique on single line towed array data to generate an estimate at the 3-D directionality at the noise field is described herein. Same results using measured data from a recent noise measurement exercise are presented and discussed.

Descriptors :   *TOWED ARRAYS, *SONAR SOUND ANALYZERS, *AMBIENT NOISE, *PASSIVE SONAR, REPRINTS, THREE DIMENSIONAL, SOUND TRANSMISSION, HORIZONTAL ORIENTATION, AZIMUTH, ACOUSTIC FIELDS.

Subject Categories : Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE