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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1994. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 96 (1994): 1033-1046, doi:10.1121/1.410380.
    Description: Using deterministic ray-acoustic modeling of 1000-km propagation in the North Pacific, a depth-dependent parameter of ocean sound channels has been found to strongly influence geometrical ray propagation. This parameter is the sound speed times the second vertical derivative of sound speed divided by the square of the first derivative. Ray and wavefront timing and intensity can be influenced within realistic ocean sound channels by unpredictable wavefront triplications and caustics. These triplications are associated with large values of the parameter at ray turning points. The parameter, a relative curvature, behaves as a random variable because of ocean finestructure, causing the unpredictability. The relative curvature has a higher mean value near the sound-speed minimum for both an internal-wave model and actual data, so that this mechanism is a plausible explanation of poor multipath resolution and identifiability late in North Pacific pulse trains.
    Description: This work was supported by the Office of Naval Technology (N00014-90-C-0098) and the Office of Naval Research, Ocean Acoustics Program (N00014-92-J-1162).
    Keywords: Pacific Ocean ; Ray-tracing ; Sound waves ; Wave propagation ; Pulses ; Acoustics ; Sound velocity ; Depth profiles ; Wave front ; Fluctuations ; Underwater
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © IEEE, 2015. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Ocean Engineering 40 (2015): 237-249, doi:10.1109/JOE.2013.2294291.
    Description: A study of sound propagation over a submarine canyon northeast of Taiwan was made using mobile acoustic sources during a joint ocean acoustic and physical oceanographic experiment in 2009. The acoustic signal levels (equivalently, transmission losses) are reported here, and numerical models of 3-D sound propagation are employed to explain the underlying physics. The data show a significant decrease in sound intensity as the source crossed over the canyon, and the numerical model provides a physical insight into this effect. In addition, the model also suggests that reflection from the canyon seabed causes 3-D sound focusing when the direction of propagation is along the canyon axis, which remains to be validated in a future experiment. Environmental uncertainties of water sound speed, bottom geoacoustic properties, and bathymetry are addressed, and the implications for sound propagation prediction in a complex submarine canyon environment are also discussed.
    Description: The Quantifying, Predicting and Exploiting (QPE) Uncertainty Initiative Experiment was supported jointly by the National Science Council, Taiwan, under Project NSC98-2623-E002-018-D and the U.S. Office of Naval Research (ONR) under Grant N00014-08-1-0763. The work of Y.-T. Lin was supported by the U.S. ONR under Grants N00014-10-1-0040 and N00014-13-1-0026. The work of T. F. Duda was supported by the U.S. ONR under Grant N00014-11-1-0194.
    Keywords: Acoustics ; Noise ; Numerical models ; Solid modeling ; Sonar equipment ; Underwater vehicles ; Vehicles
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-05-26
    Description: A three-dimensional (3D) parabolic equation acoustical propagation code has been developed and run successfully. The code is written in the MATLAB language and runs in the MATLAB environment. The code has been implemented in two versions, applied to (1) Horizontal low-frequency (100 to 500 Hz) propagation through the shallow water waveguide environment; (2) Vertical high-frequency propagation (6 to 15 kHz) to study normal-incidence reflection from the lower side of the ocean surface. The first edition of the code reported on here does not implement refinements that are often found in 2D propagation models, such as allowing density to vary, optimally smoothing soundspeed discontinuities at the water/seabed interface, and allowing an omni-directional source. The code is part of a development effort to test the applicability of 2D (and N by 2D) models, which have more refinements than this model, to the study of fully 3D propagation problems, such as sound transiting steep nonlinear coastal-area internal waves and/or sloping terrain, and to provide a numerical tool when the full 3D solution is needed.
    Description: Funding was provided by the Office of Naval Research under Contract No. N00014-05-1-0482.
    Keywords: Acoustics ; Numerical simulation ; Fourier split step
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 5717685 bytes
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