Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves

Gong, Zheng; Chen, Tianrun; Ratilal, Purnima; Makris, Nicholas C.

doi:10.1121/1.4824157

Cited by 8 publications

(12 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The formulation used here for modeling attenuation combines waveguide scattering theory [7,8] and a differential slab marching approach introduced by Rayleigh for the mean field to derive the first two statistical moments of the acoustic field in a waveguide with inhomogeneities [5]. This formulation has been previously shown to be consistent with experimental measurements of attenuation and temporal coherence loss in the presence of internal waves for both mid-frequency signals (415 Hz) in a continental shelf environment and low-frequency signals (10-70 Hz) in a deep ocean waveguide [9][10][11].…”

Section: Introductionmentioning

confidence: 81%

“…Scattering strength and attenuation are modeled for each fish species and environment and we search for the sensing frequency that maximizes scattering strength uncorrected for two-way attenuation from fish (SS − ∆SPL 2way ), which in turn maximizes the detection range of the sensing system. Here SS is modeled using Equation (15) and ∆SPL 2way is modeled using Equation (11).…”

Section: Attenuation Prediction and Frequency Selectionmentioning

confidence: 99%

See 1 more Smart Citation

The Effect of Attenuation from Fish Shoals on Long-Range, Wide-Area Acoustic Sensing in the Ocean

et al. 2019

Self Cite

View full text Add to dashboard Cite

Acoustics is the primary means of long-range and wide-area sensing in the ocean due to the severe attenuation of electromagnetic waves in seawater. While it is known that densely packed fish groups can attenuate acoustic signals during long-range propagation in an ocean waveguide, previous experimental demonstrations have been restricted to single line transect measurements of either transmission or backscatter and have not directly investigated wide-area sensing and communication issues. Here we experimentally show with wide-area sensing over 360 • in the horizontal and ranges spanning many tens of kilometers that a single large fish shoal can significantly occlude acoustic sensing over entire sectors spanning more than 30 • with corresponding decreases in detection ranges by roughly an order of magnitude. Such blockages can comprise significant impediments to underwater acoustic remote sensing and surveillance of underwater vehicles, marine life and geophysical phenomena as well as underwater communication. This makes it important to understand the relevant mechanisms and accurately predict attenuation from fish in long-range underwater acoustic sensing and communication. To do so, we apply an analytical theory derived from first principles for acoustic propagation and scattering through inhomogeneities in an ocean waveguide to model propagation through fish shoals. In previous experiments, either the attenuation from fish in the shoal or the scattering cross sections of fish in the shoal were measured but not both, making it impossible to directly confirm a theoretical prediction on attenuation through the shoal. Here, both measurements have been made and they experimentally confirm the waveguide theory presented. We find experimentally and theoretically that attenuation can be significant when the sensing frequency is near the resonance frequency of the shoaling fish. Negligible attenuation was observed in previous low-frequency ocean acoustic waveguide remote sensing (OAWRS) experiments because the sensing frequency was sufficiently far from the swimbladder resonance peak of the shoaling fish or the packing densities of the fish shoals were not sufficiently high. We show that common heuristic approaches that employ free space scattering assumptions for attenuation from fish groups can lead to significant errors for applications involving long-range waveguide propagation and scattering.

show abstract

Section: Introductionmentioning

confidence: 81%

Section: Attenuation Prediction and Frequency Selectionmentioning

confidence: 99%

The Effect of Attenuation from Fish Shoals on Long-Range, Wide-Area Acoustic Sensing in the Ocean

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…The modeled coherence time scale of narrow-band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, to decrease with increasing internal wave energy, and to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments (Gong et al, 2013). The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging.…”

Section: Work Completedmentioning

confidence: 99%

“…A paper on the topic of acoustic field temporal coherence time scales in internal-wave filled continental-shelf waveguides has been finished (Gong et al, 2013). Coherence times for order 400-Hz sound are predicted to range from roughly 2 to 20 minutes depending upon environmental conditions.…”

Section: Stochastic Acoustic Modeling (Makris)mentioning

confidence: 99%

Integrated Modeling and Analysis of Physical Oceanographic and Acoustic Processes

Duda

Lynch²,

Lin³

et al. 2013

Self Cite

View full text Add to dashboard Cite

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

show abstract

“…Ensembles of dynamical ocean models that are properly formulated for specific dynamical processes can also be used to define the statistics of those processes. Statistics of the acoustic field can be computed and then examined by feeding the ocean statistics (model-or data-derived) into statistical acoustic models (Flatté et al 1979;Colosi and Morozov 2009;Colosi et al 2012bColosi et al , 2013Gong et al 2013;White et al 2013;Raghukumar and Colosi 2014;Rouseff and Lunkov 2015;Colosi 2016).…”

Section: Statistical Ocean Model and Statistical Acoustics Modelmentioning

confidence: 99%

Modeling and Forecasting Ocean Acoustic Conditions

Duda¹

2017

j mar res

View full text Add to dashboard Cite

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.

show abstract

Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves

Cited by 8 publications

References 40 publications

The Effect of Attenuation from Fish Shoals on Long-Range, Wide-Area Acoustic Sensing in the Ocean

The Effect of Attenuation from Fish Shoals on Long-Range, Wide-Area Acoustic Sensing in the Ocean

Integrated Modeling and Analysis of Physical Oceanographic and Acoustic Processes

Modeling and Forecasting Ocean Acoustic Conditions

Contact Info

Product

Resources

About