Accession Number : ADA018774

Title :   The Time-Scale of the Fluctuation of a Bottom Bounce Narrow-Band Signal from a Moving Source in the Sea.

Descriptive Note : Technical rept.,

Corporate Author : NAVAL SURFACE WEAPONS CENTER WHITE OAK LAB SILVER SPRING MD

Personal Author(s) : Urick,R. J.

Report Date : 25 JUN 1975

Pagination or Media Count : 25

Abstract : The time scale, or time for the auto-correlation coefficient to fall to l/e, of the fluctuations of the sound from a low frequency moving source has been found to range from a fraction of a minute to about 10 minutes. Computer-produced correlograms were obtained from recordings of signals received over bottom bounce paths out to the first convergence zone, using sample integration times ranging from 10 seconds to 5 minutes in length. The correlation times of sample groups 40 minutes long were found to be highly variable from group to group; over such intervals the temporal statistics of the fluctuation appear essentially non-stationary, perhaps because of multipath reflection and scattering from different portions of a spatially variable ocean floor, over which the source travels toward or away from a stationary receiver. There is a suggestion in the data that the correlation time increases with range of the source, but there is no indication that it varies with source speed. Controlled experiments on this virgin subject are required. (Author)

Descriptors :   *Underwater sound, *Sound transmission, Bottom bounce, Multipath transmission, Signals, Moving targets, Narrowband, Variations, Convergence zone, Autocorrelation, Ocean bottom, Scattering, Reflection

Subject Categories : Acoustic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE