摘要 :
Our long-term goal is to improve sonar performance through interpretation of geological data and high-frequency acoustic modeling. This work should improve understanding of the variability of the salient geoacoustic properties of ...
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Our long-term goal is to improve sonar performance through interpretation of geological data and high-frequency acoustic modeling. This work should improve understanding of the variability of the salient geoacoustic properties of the sea floor that control acoustic propagation and scattering.
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摘要 :
The long-term goal of this project is to develop efficient inversion algorithms for successful geoacoustic parameter estimation, inversion for sound- speed in the water-column, and source localization, exploiting (fully or partial...
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The long-term goal of this project is to develop efficient inversion algorithms for successful geoacoustic parameter estimation, inversion for sound- speed in the water-column, and source localization, exploiting (fully or partially) the physics of the propagation medium. Algorithms are designed for inversion via the extraction features of the acoustic field and optimization. The potential of analytic approaches also is investigated. Our specific objectives are as follows: (1) Achieve accurate and computationally efficient inversion for propagation medium parameters and source localization by designing estimation schemes that combine acoustic field and statistical modeling, (2) Develop methods for passive localization and inversion of environmental parameters that select features of propagation that are essential to model for accurate inversion, (3) Implement Bayesian filtering methods that provide dynamic and efficient solutions for the first two objectives, and (4) Develop analytic techniques for sediment sound speed estimation. Continuing efforts from previous years, we worked with Bayesian approaches applied to sound signals for the extraction of acoustic features using a combination of physics and statistical signal processing. One of the topics approached this past year was source localization, bathymetry, and water column sound speed estimation using arrival time estimates for propagation in multipath environments with sequential Monte Carlo methods, tied with a linearization method with novel features. The initial goal is to estimate accurately the arrival times of sound paths in shallow water environments. Then, we propagate these arrival times and their posterior PDFs through a quasilinear model for source location, bathymetry, and water column sound speed profile estimation. Finally, we worked on a new sediment sound speed estimation scheme based on Stickler's inverse problem approach.
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摘要 :
Physically sound models of acoustic interaction with the ocean floor including penetration, reflection and scattering in support of MCM and ASW needs. The objectives are to fill important gaps in our knowledge and understanding of...
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Physically sound models of acoustic interaction with the ocean floor including penetration, reflection and scattering in support of MCM and ASW needs. The objectives are to fill important gaps in our knowledge and understanding of ocean sediment acoustics, including (1) a new model to account for the recently measured low-frequency sound speed anomaly, (2) new scattering mechanisms to augment current Navy models of high-frequency bottom scattering, and (3) the study of time dependent propagation and scattering effects due to shallow water gas bubbles in the sediment.
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摘要 :
Shallow Water 2006 experiment was conducted in a region off the New Jersey coast where nonlinear internal wave activity is known to occur and this resulting in range-dependent sound speed profiles in the water column. In continuat...
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Shallow Water 2006 experiment was conducted in a region off the New Jersey coast where nonlinear internal wave activity is known to occur and this resulting in range-dependent sound speed profiles in the water column. In continuation of the work on estimation of range-dependent sediment compressional wave speed profiles, the ability to use data similar to that collected during the shallow water experiment to determine the range-dependent sound speed profiles in the water column due to the presence of internal waves is explored. It is shown that range-dependent sound speed profiles in the water column can be obtained assuming that the sediment characteristics are known. During 2011 a series of experiments were conducted off the coast of New Jersey. The primary objective of this experiment was to evaluate the possibility of determining the sediment acoustic properties by the use of air launched sonobuoys such as those used ASW operations. It is shown that such a system can be used to extract the sediment acoustic properties. The methods can be adopted to characterize the range dependent environment namely the water column and the sediment.
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摘要 :
The goal of this research is to understand the effects of range-dependent sediment properties on the acoustic field in 2-D shallow water environments. This information, in part, is required to solve the statistical inference probl...
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The goal of this research is to understand the effects of range-dependent sediment properties on the acoustic field in 2-D shallow water environments. This information, in part, is required to solve the statistical inference problem in inhomogeneous shallow water environments. The spatio-temporal variability of the water column needs to be properly accounted for while looking for the effect of range-dependent sediment properties on the acoustic field. The objective of the current work is to create a high-fidelity model of the water column along a single propagation track for the Shallow Water 2006 (SW06) experiment. The water column model is constructed from oceanographic data measured at moorings located along the acoustic propagation track. The water column model describes oceanographic features on several space-time scales, including those ranging from frontal boundaries to nonlinear internal waves. The purpose of the water column model is to reduce the mismatch between measured and modeled acoustic data so that other propagation effects, such as range-dependent sediment properties can be investigated in the future.
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摘要 :
Our long-term objective is to establish a database of sediment and bottom properties including sediment compressional wave speed, shear wave speed, attenuation and density. Using this we propose to provide the best sediment model ...
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Our long-term objective is to establish a database of sediment and bottom properties including sediment compressional wave speed, shear wave speed, attenuation and density. Using this we propose to provide the best sediment model for any region with estimates of model uncertainty. These data would be appropriate for incorporation in state-of-the-art propagation models for acoustic effects prediction on the marine environment.
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摘要 :
The primary long term objective of this project remains: To provide a real-time, area-wide technique in shallow water for the estimation of volumetric (3-D) geoacoustic parameters. These parameters are vital inputs for SONAR model...
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The primary long term objective of this project remains: To provide a real-time, area-wide technique in shallow water for the estimation of volumetric (3-D) geoacoustic parameters. These parameters are vital inputs for SONAR models (and subsequent signal processing and target localization methods) and include: geometric values (such as source location, array element location, and water depths) as well as bottom properties (such as sediment layer thicknesses, sound-speed profiles, densities, and attenuations). This area- wide estimation would be made via multiple air-deployed receiver arrays and multiple broadband air-deployed low frequency sources. The objectives of this second year's work included: (1) Investigation of array configurations (phone depths and ranges). No sensors were applied to Haro Strait arrays to give information on phone locations. Thus, what happens when unknown array parameters are simply added to the overall parameter search space; (2) Broadband (BB) inversion using MFP (with 4 frequencies all of which must have Bartlett values greater than 0.90 at each frequency). Will 4 frequencies be sufficient to allow GI convergence to a solution, even for simulated data; (3) Consideration of concurrent multiple sources for GI. What can we gain by the consideration of more than one source for an inversion; and (4) Demonstration of a full tomographic inversion of Haro St. data.
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