Accession Number : ADA299769

Title :   Operation Rocky Road: Three-Dimensional Noise Field Directionality Estimation.

Descriptive Note : Final rept.,

Corporate Author : NAVAL RESEARCH LAB STENNIS SPACE CENTER MS

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

PDF Url : ADA299769

Report Date : 06 OCT 1995

Pagination or Media Count : 57

Abstract : For many reasons, the three dimensional (3D) arrival structure of the undersea ambient noise field is of interest to the research and development community. One is that the arrival structure can be used to estimate the beam noise of an array, which may be required to estimate the performance of 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 of the acoustic propagation along the azimuths of 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 of the noise sources. Both of these classes of clues are important in the verification and validation of undersea ambient noise models. The ideal measurement tool to measure the 3D arrival structure of the noise field is a high resolution volumetric array sonar system. Unfortunately, such a system is n0t generally available. However, towed horizontal line arrays are avallable 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 an elevation angle of 0 deg, the vertical character of 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 of the 3D directionality of the noise field can be obtained. An algorithm that uses such a technique on single-line towed array data to generate an estimate of the 3D directionality of the noise field is described herein. Some results using measured data from the ROCKY ROAD MILOC exercise are presented and discussed.

Descriptors :   *UNDERWATER ACOUSTICS, *NOISE(SOUND), ALGORITHMS, VERIFICATION, VALIDATION, TOWED ARRAYS, ANGLE OF ARRIVAL, SOUND TRANSMISSION, ACOUSTIC MEASUREMENT, HORIZONTAL ORIENTATION, LINEAR ARRAYS, AZIMUTH, AMBIENT NOISE, CONICAL BODIES, ACOUSTIC FIELDS, RADIATION PATTERNS.

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE