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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

Noise background levels and noise event tracking/characterization under the Arctic ice pack: Experiment, data analysis, and modeling

Williams, K.L., M.L. Boyd, A.G. Soloway, E.I. Thorsos, S.G. Kargl, and R.I. Odom, "Noise background levels and noise event tracking/characterization under the Arctic ice pack: Experiment, data analysis, and modeling," IEEE J. Ocean. Eng., 43, 145-159, doi:10.1109/JOE.2017.2677748, 2018.

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1 Jan 2018

In March 2014, an Arctic Line Arrays System (ALAS) was deployed as part of an experiment in the Beaufort Sea (approximate location 72.323 N, 146.490 W). The water depth was greater than 3500 m. The background noise levels in the frequency range from 1 Hz to 25 kHz were measured. The goal was to have a three-dimensional sparse array that would allow determination of the direction of sound sources out to hundreds of kilometers and both direction and range of sound sources out to 1–2 km from the center of the array. ALAS started recording data at 02:12 on March 10, 2014 (UTC). It recorded data nearly continuously at a sample rate of 50 kHz until 11:04 on March 24, 2014. Background noise spectral levels are presented for low and high floe-drift conditions. Tracking/characterization results for ice-cracking events (with signatures typically in the 10–2000-Hz band), including the initiation of an open lead within about 400 m of the array, and one seismic event (with a signature in the 1–40-Hz band) are presented. Results from simple modeling indicate that the signature of a lead formation may be a combination of both previously hypothesized physics and enhanced emissions near the ice plate critical frequency (where the flexural wave speed equals that of the water sound speed). For the seismic event, the T-wave arrival time results indicate that a significant amount of energy coupled to T-wave energy somewhere along the path between the earthquake and ALAS.

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.

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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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