Statistics of acoustic pulse signals through nonlinear waves on the continental shelf of the northeastern South China Sea
Reeves, Justin M.
MetadataShow full item record
1 km), high-frequency, nonlinear internal depression and elevation waves superimposed on the internal tides. Through the use of an empirical sound-speed field and a coupled, normal-mode acoustic propagation model, the phenomenology of the nonlinear internal wave field upon the observed intensity pattern was examined. Analysis of the observed and modeled acoustic intensity time-series indicates that the long-wave pattern dictates, to a large degree, the temporal changes in the vertical structure of the sound intensity level. Furthermore, both measurement and model results show that when the thermocline was rapidly displaced by the nonlinear internal waves, sound intensity fluctuations reached their maximum. Modeling results suggest that these maximums are due to the scattering of acoustic energy into both higher and lower acoustic modes along the edges of the elevation/depression waves where strong horizontal sound-speed gradients were present. An additional goal of this paper is to propose and validate an extended statistical theory that relates the observed statistics of the acoustic intensity to the number of resolvable arrivals. The number of resolvable arrivals depends on signal bandwidth and the criteria of "well separateness" and was found to vary significantly as the nonlinear internal waves evolve along the transmission path. The theory is found to be pertinent when the temporal length of the window for calculating statistics was expanded sufficiently in order to collect a sample population with the following characteristics: 1) the standard deviation of the estimated number of arrivals is small, and 2) sufficient internal wave events are captured to ensure the phase distribution of the arrivals in the sample population is uniform.
Showing items related by title, author, creator and subject.
Chen, Meihuei (Monterey, California: Naval Postgraduate School, 2016-03);During the Windy Islands Soliton Experiment, two deep water moorings were deployed 167 km apart in the northeastern South China Sea (SCS) basin to study the effects of nonlinear internal waves on 400- Hz acoustic signal ...
Coby, Weston R. T.; Fischer, Jacob A. (Monterey, California: Naval Postgraduate School, 2013-09);In 2009, a monthlong study was conducted in the Western Philippine Sea. This experiment collected oceanographic and acoustic data from two moorings, the Distributed Vertical Line Array (DVLA) and T1 moorings. The T1 mooring ...
Ceschini, Joseph J. (Monterey, California: Naval Postgraduate School, 2013-06);The objective of this research is to model and study the effects of transbasin internal waves on low-frequency signal transmission through the South China Sea (SCS) basin. Specifically, the fluctuations in the multipath ...