Ambient noise and signal uncertainties during the summer shelfbreak primer exercise

Thumbnail Image
Files
Chiu_Ambient_2002.pdf (1003.18 KB)
Authors
Abbot, Philip
Gedney, Charles
Dyer, Ira
Chu, Ching-Sang
Subjects
Advisors
Date of Issue
2002
Date
Publisher
Language
Abstract
Uncertainties in noise Ievel, andin signallevel after long-range (42 km) acoustic shallow water transmissions, from a pulsed source, are determined from the summer shelfbreak PRIMER experiment. Fluctuations over the 1 0-day period are not stationary, but are rendered so by tracking the wandering of their means. Then narrow-sense stationary probability density functions are obtained of ambient noise and signal peak transmissions from a match-filter output with time-bandwidth product = 1. The data are centered at 400 Hz, in a 100 Hz bandwidth, and analyzed from three individual hydrophones of a vertical line array. The ambient noise fluctuations closely follow the phase-random Log-Rayleigh density, with standard deviation cr = 5.6 dB. Signal peak statistics are determined from demeaned 50 s samples. The signal statistics over an 8-h period are approximately similar, but not identical, to those over the entire 10-day period. The signal has narrower histograms (cr "' 0.8 dB) than the noise. Log Chi-Square densities, fit to the signal histograms, suggest that about 30 equal intensity components contribute to the fluctuations, many more than can be attributed to the idealized modal structure in the shelfbreak duct. This suggests that either strong scattering affects the signal transmission, or the signal process is not fully phase-random.
Type
Article
Description
URI
https://hdl.handle.net/10945/43433
Series/Report No
Department
Organization
Identifiers
NPS Report Number
Sponsors
Funder
Format
Citation
N. G. Pace and F.B. Jensen (eds.), Impact of Littoral Environmental Variability an Acoustic Predictions and Sonar Performance, 255-262.
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Collections
Publications