Accession Number : ADA327901

Title :   Performance of Acoustic Tracking Arrays in Atmospheric Turbulence.

Descriptive Note : Final rept. 1 May-14 Jun 96,

Corporate Author : ARMY RESEARCH LAB ADELPHI MD

Personal Author(s) : Wilson, David K.

PDF Url : ADA327901

Report Date : JUL 1997

Pagination or Media Count : 47

Abstract : A method is described for assessing the performance of acoustic arrays used to determine source bearings. The method involves calculation of the Cramer-Rao lower bound (CRLB), which characterizes the best performance obtainable for a given array configuration and set of operating conditions. The CRLB calculations are used to show that the performance of the arrays depends on the sensor configuration, the acoustic frequency, the distance from the source, the background noise, and atmospheric turbulence. Near to the source, and at low frequencies, it is the background noise that limits array performance. Turbulence becomes the limiting factor as the distance and frequency are increased. When performance is limited by turbulence, the calculations are found to be very sensitive to the particular turbulence model used. The von Karman type of model appears to provide the most reasonable CRLB calculations. The turbulent degradation is found to result primarily from small-scale fluctuations in the wind velocity. Performance predictions for ARL's Remote Netted Acoustic Detection System (RNADS) are presented; it is found that RNADS should provide angle-of-arrival (AOA) accuracy of several degrees or better for signal-to-noise ratios above 10 dB during most atmospheric turbulence conditions.

Descriptors :   *ACOUSTIC ARRAYS, *ACOUSTIC TRACKING, SIGNAL TO NOISE RATIO, ANGLE OF ARRIVAL, BEARING(DIRECTION), ACOUSTIC DETECTION, TURBULENCE, SOUND TRANSMISSION, WIND VELOCITY, ATMOSPHERIC REFRACTION, BACKGROUND NOISE, WAVEFRONTS, CROSS CORRELATION.

Subject Categories : Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE