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Approved for public release; distribution is unlimited. / Current underwater acoustic communication systems operate in the frequency band of 1 - 10 kHz and utilize various forms of signal processing to improve data rates. In this work, the influence of the environment on long-range propagation of acoustic signals will be examined over the band of 1-5 kHz. The transmission loss (Th) as a function of range over the bandwidth will be one measure to determine the optimal operating character of the communications channel. Additionally, estimates of signal variance over the bandwidth as a function of range will be computed. The variance will be generated from source platform motion and interface roughness. Particular attention will be paid to the 2 - 4 kHz band of certain operating systems for long-range transmission / Lieutenant, United States Navy

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Charles W. Therrien, Kevin B. Smith. Includes bibliographical references (p. 147-149). Also available online.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Roberto Cristi, Joseph Rice. Includes bibliographical references (p. 129-130). Also available online.

Thesis (M.S. in Engineering Acoustics) Naval Postgraduate School, March 2001. / Thesis advisor(s): Smith, Kevin B. ; Nagle, Daniel T. "March 2001." Includes bibliographical references (p. 39-40). Also Available in print.

Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, June 2010. / Thesis Advisor(s): Rice, Joseph A. "June 2010." Description based on title screen as viewed on July 13, 2010. Author(s) subject terms: Communications network, sensor network, acoustic communications, undersea sensors, simulation, Seastar, Seaweb Includes bibliographical references (p. 89-90). Also available in print.

Two areas of underwater acoustics are investigated: ocean-bottom scattering and acoustic fields in geometrically dispersive sound channels. The purpose is to describe and provide an understanding of the physical mechanisms in these two areas by comparing analyzed results from ocean experiments with theoretical computations. Experiments using directive 19.5-kHz transducers illustrate temporal and spacial behavior of signals scattered from the ocean bottom. The signals fluctuate, as a function of acoustic geometry, in linear relation to source and receiver motion and to signal frequency. Spacial structure of the acoustic field depends on frequency and acoustic geometry and is independent of motion and bottom roughness. Data supporting these observations are included as well as data showing the effects of bottom type on the scattered returns, that is, the existence of subbottom returns in some data. Volume-scattering-strength profiles are also provided from data obtained in these experiments. Continuous-wave (CW) and impulsive sources covering frequencies 5 to 260 Hz were towed and deployed respectively over ranges up to 3000 km, with reception on fixed hydrophones. Analyses of measured propagation losses of these low-frequency acoustic signals in the dispersive channel provide insights into the nature of the propagation and the acoustic channel. Both the CW signals and the arrivals of the impulsive signals are analyzed in terms of transmission loss, convergence-zone structure, source-motion effects, interference structure, and channel characteristics. The systematic variation (internal tides) of the medium and its influence on the interference field are discussed. The state of modeling, both simple and complicated, is reviewed and compared with results of the ocean experiments. Relationships are provided between this work and the broader field of underwater acoustics. Suggested areas for future research are made.

No description available.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Charles W. Therrien, Murali Tummala. Includes bibliographical references (p. 83-84). Also available online.

Thesis (M.S. in Electrical Engineering and M.S. in Engineering Acoustics)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Roberto Cristi, Kevin B. Smith. Includes bibliographical references (p. 91-94). Also available online.