Acoustic multipath arrivals in the horizontal plane due to approaching nonlinear internal waves

Badiey, Mohsen; Katsnelson, Boris; Lin, Ying‐Tsong; Lynch, James F.

doi:10.1121/1.3553374

Cited by 44 publications

(28 citation statements)

References 7 publications

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“…(In that situation, knowing seafloor properties is as critical as knowing the nature of the refraction within the water if a fully quantitative result is desired, but here behavior of the water column is emphasized). Simultaneous fluctuating refraction in both the vertical and horizontal planes by nonlinear internal gravity waves (Apel et al 2007) also can lead to temporally and spatially dependent attenuation, focusing, and multipath (Badiey et al 2005;Lynch et al 2010;Badiey et al 2011;Duda et al 2011aDuda et al , 2012. These studies show that such waves can cause rapid and dramatic changes to sound fields in the ocean as the internal waves themselves propagate and evolve.…”

Section: Propagation Regimes and Scattering Regimesmentioning

confidence: 98%

“…On the other hand, under strong scattering sound can be drastically redirected, with the incident field significantly altered. Recent analysis of many ocean propagation scenarios tells us that strong scattering is expected in many situations, particularly for sound passing through strong nonlinear internal wave packets in shallow water (Badiey et al 2005(Badiey et al , 2011(Badiey et al , 2013Lynch et al 2010;Duda et al 2011aDuda et al , 2012. A few images of fields undergoing strong scattering appear in Section 4.…”

Section: Propagation Regimes and Scattering Regimesmentioning

confidence: 99%

“…Figures 4 and 5 illustrate fields used in process studies of sound in isolated strong internal waves. Process studies, showing interesting results regarding the structure of ducted and redirected sound energy, are numerous (Badiey et al 2011;McMahon et al 2012;Lin et al 2013b). …”

Section: E Analytic Feature Model and Acoustics Modelmentioning

confidence: 99%

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Modeling and Forecasting Ocean Acoustic Conditions

Duda¹

2017

j mar res

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Modeling acoustic conditions in an oceanic environment is a multiple-step process. The environmental conditions (features) in the area first must be measured or estimated; relevant features include seabed geometry, seabed composition, and four-dimensionally (4D) variable sound-speed and density variations related to evolving or wave motions. Often the dynamical wave modeling depends on first obtaining correct seabed and mean stratification conditions (for example, nonlinear internal wave modeling). Next, this information must be included in sound propagation modeling. A selection of the many methods and tools available for these tasks are described, with a focus on modeling sounds of 20 to 1000 Hz propagating through water-column features that are time-dependent and variable in three dimensions (i.e., 4D variable). An example of a 3D parabolic equation acoustic calculation shows how variability caused by evolving internal tidal waves affects sound propagation. Different propagation and scattering regimes are discussed, including the theoretically delineated weak scattering and strong scattering regimes, as well as the empirically examined regime found in nonlinear internal waves. The histories and the current state of our oceanographic knowledge (the input to acoustic modeling) and of our ability to effectively model complex acoustic conditions are discussed. Example acoustic simulation applications are also discussed; these are ocean acoustic tomography, coherence prediction, and signal-to-noise ratio prediction. Types of ocean models and acoustic models and how they are interfaced are also examined. These include deterministic, statistical analytic feature models.

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Section: Propagation Regimes and Scattering Regimesmentioning

confidence: 98%

Section: Propagation Regimes and Scattering Regimesmentioning

confidence: 99%

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Modeling and Forecasting Ocean Acoustic Conditions

Duda¹

2017

j mar res

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“…As before, we use the background water column model from previous examples and its perturbation due to a twenty-five meter internal wave. processing of the SW06 data [46,15]. Our goal in this section is to study the effects of mode coupling accompanying the HLM.…”

Section: Horizontal Lloyd's Mirrormentioning

confidence: 99%

“…al. [15] performed careful modal and frequency decomposition of the NRL300 signal on the August 17, during another time of strong internal wave activity, and registered two distinct arrivals for certain modes, clearly indicating the out of vertical plane acoustic propagation.…”

Section: Observationsmentioning

confidence: 99%

Three-dimensional acoustic propagation through shallow water internal, surface gravity and bottom sediment waves

Shmelev¹

2011

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This thesis describes the physics of fully three-dimensional low frequency acoustic interaction with internal waves, bottom sediment waves and surface swell waves that are often observed in shallow waters and on continental slopes. A simple idealized model of the ocean waveguide is used to analytically study the properties of acoustic normal modes and their perturbations due to waves of each type. The combined approach of a semi-quantitative study based on the geometrical acoustics approximation and on fully three-dimensional coupled mode numerical modeling is used to examine the azimuthal dependence of sound wave horizontal reflection from, transmission through and ducting between straight parallel waves of each type. The impact of the natural crossings of nonlinear internal waves on horizontally ducted sound energy is studied theoretically and modeled numerically using a three-dimensional parabolic equation acoustic propagation code. A realistic sea surface elevation is synthesized from the directional spectrum of long swells and used for three-dimensional numerical modeling of acoustic propagation. As a result, considerable normal mode amplitude scintillations were observed and shown to be strongly dependent on horizontal azimuth, range and mode number. Full field numerical modeling of low frequency sound propagation through large sand waves located on a sloped bottom was performed using the high resolution bathymetry of the mouth of San Francisco Bay. Very strong acoustic ducting is shown to steer acoustic energy beams along the sand wave's curved crests.

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