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Steve Kargl

Senior Principal Physicist

Email

kargl@apl.washington.edu

Phone

206-685-4677

Research Interests

Physical Acoustics

Biosketch

Dr. Kargl works on theoretical and experimental physical acoustics. His past studies have focused on the scattering of sound from submerged targets, scattering from targets embedded in a poroelastic medium, measurement and modeling of ambient noise in shallow water environments, and wave propagation in stratified media with emphasis on propagation in shallow water waveguides. He is currently working on problems associated with bubbles in marine sediments and nonlinear wave propagation from focused sources. He has recently developed an interest in compressional shock-wave propagation in a saturated poroelastic medium. Dr. Kargl joined APL in 1993.

Department Affiliation

Acoustics

Education

B.S. Physics & Mathematics, University of Dayton, 1985

M.S. Physics, Washington State University, 1987

Ph.D. Physics, Washington State University, 1990

Projects

Synthetic Aperture Sonar (SAS) and Acoustic Templates for the Detection and Classification of Underwater Munitions

During Pond Experiment 2010 (PondEx10), acoustic responses from four inert unexploded ordnances (UXO), 5 scientific targets (solid cylinders, pipes, and replica of a UXO), and two rocks were collected at the test pond facility of the Naval Surface Warfare Center, Panama City Division (NSWC PCD).

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During Pond Experiment 2010 (PondEx10), acoustic responses from four inert unexploded ordnances (UXO), 5 scientific targets (solid cylinders, pipes, and replica of a UXO), and two rocks were collected at the test pond facility of the Naval Surface Warfare Center, Panama City Division (NSWC PCD). The UXO were either proud on a flat water-sediment interface, buried just beneath the sediment interface, or partially buried. Synthetic aperture sonar (SAS) data were taken for several orientations of the UXO with respect to the path of the SAS platform. The steep grazing angle permitted an acoustic field to penetrate to buried targets via ordinary refraction, while at a shallow grazing angles only proud targets were interrogated. Two frequency bands were used to span a 1 to 50 kHz range. SAS images for the targets at various orientations are displayed. The reduction of data sets to acoustic templates is shown. Acoustic templates provide a possible means to classify a detected object as a UXO-like target.

Publications

2000-present and while at APL-UW

Scattering from a finite cylindrical target in a waveguide

Kargl, S.G., T. Shim, K. Williams, and S. Im, "Scattering from a finite cylindrical target in a waveguide," Proc., MTS/IEEE OCEANS Conference, 19-23 September, Monterey, CA, doi:10.1109/OCEANS.2016.7761277 (IEEE, 2016).

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1 Dec 2016

Detection of an object in shallow water has seen a resurgence in importance due to concerns for harbor security. When the horizontal range to an object is large compared to the nominal water depth, then the response of an object to active sonar must necessarily include possible interactions with the boundaries of the waveguide. As an initial step toward the development of detection algorithms, we consider an object in a homogeneous waveguide with planar boundaries. Reflection of the transmitter, receiver, and their images through boundaries allows the scattering problem to be recast into a superposition of many free field scattering problems. An overview of our model and its application to a cylindrical target in littoral waters are given.

Underwater UXO classification using Matched Subspace Classifier with synthetic sparse dictionaries

Hall, J.J., M.R. Azimi-Sadjadi, S.G. Kargl, "Underwater UXO classification using Matched Subspace Classifier with synthetic sparse dictionaries," Proc., MTS/IEEE OCEANS, 19-23 September, Monterey, CA, doi:10.1109/OCEANS.2016.7761016 (IEEE, 2016).

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1 Dec 2016

This paper is concerned with the development of a system for the classification of military munitions and unexploded ordnance (UXO) in shallow underwater environments. A Matched Subspace Classifier (MSC) is used in conjunction with Acoustic Color (AC) features generated from the raw sonar returns for munition characterization. Our classification hypothesis is that spectral content of the sonar backscatter display unique acoustic signatures providing good discrimination between different classes of detected contacts. The system is exclusively trained using synthetic sonar data and then tested using real data sets collected from a side-looking sonar system. These data sets were collected using underwater objects in relatively controlled and clutter-free environments. Classification results are presented using standard performance metrics such as probability of correct classification (PCC), probability of false alarm (PFA) in Receiver Operating Characteristic (ROC) curves, and confusion matrices.

Scattering from objects at a water–sediment interface: Experiment, high-speed and high-fidelity models, and physical insight

Kargl, S.G., A.L. España, K.L. Williams, J.L. Kennedy, and J.L. Lopes, "Scattering from objects at a water–sediment interface: Experiment, high-speed and high-fidelity models, and physical insight," IEEE J. Ocean. Eng., 40, 632-642, doi:10.1109/JOE.2014.2356934, 2015.

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1 Jul 2015

In March 2010, a series of measurements were conducted to collect synthetic aperture sonar (SAS) data from objects placed on a water-sediment interface. The processed data were compared to two models that included the scattering of an acoustic field from an object on a water-sediment interface. In one model, finite-element (FE) methods were used to predict the scattered pressure near the outer surface of the target, and then this local target response was propagated via a Helmholtz integral to distant observation points. Due to the computational burden of the FE model and Helmholtz integral, a second model utilizing a fast ray model for propagation was developed to track time-of-flight wave packets, which propagate to and subsequently scatter from an object. Rays were associated with image sources and receivers, which account for interactions with the water-sediment interface. Within the ray model, target scattering is reduced to a convolution of a free-field scattering amplitude and an incident acoustic field at the target location. A simulated or measured scattered free-field pressure from a complicated target can be reduced to a (complex) scattering amplitude, and this amplitude then can be used within the ray model via interpolation. The ray model permits the rapid generation of realistic pings suitable for SAS processing and the analysis of acoustic color templates. Results from FE/Helmholtz calculations and FE/ray model calculations are compared to measurements, where the target is a solid aluminum replica of an inert 100-mm unexploded ordnance (UXO).

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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