Accession Number : AD0759476

Title :   Spectral Estimation of Radiated Noise in the Near Field,

Corporate Author : HUGHES AIRCRAFT CO FULLERTON CALIF GROUND SYSTEMS GROUP

Personal Author(s) : Murphy,Donald A. ; Rockmore,Anthony J. ; Bershad,Neil J.

Report Date : 23 FEB 1973

Pagination or Media Count : 61

Abstract : Estimates of the properties of the sound field radiated from underwater sources can be made more accurately in the near field than in the far field where there is a lower signal-to-noise ratio and distortion by the medium. The more complicated processing required is analyzed by using statisticalvarious theory. This theory is reviewed to show relationships between various estimation criteria. The Cramer Rao lower bound (CRLB) is used as a standard of performance and maximum likelihood estimates (MLE) are calculated because their performance approaches this bound for large time-bandwidth products. Far-field procedures for estimating power spectra are presented since they can be extended to near-field measurements. Many procedures are currently capable of estimating the time wave-form but must be extended to estimate power spectra. These include the general estimation procedure of Banges and Schultheiss and adaptive gradient descent algorithms. (Author Modified Abstract)

Descriptors :   (*UNDERWATER SOUND, POWER SPECTRA), INFORMATION THEORY, STOCHASTIC PROCESSES, PROBABILITY DENSITY FUNCTIONS, HYDROPHONES, NOISE, CORRELATION TECHNIQUES, TRANSFORMATIONS(MATHEMATICS)

Subject Categories : Cybernetics
      Acoustic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE