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Eric Thorsos

Sr. Principal Physicist--Retiree

Affiliate Associate Professor, Electrical Engineering





Research Interests

Shallow Water Acoustic Propagation, Sediment Acoustics, Rough Surface Scattering


Dr. Thorsos research addresses high-frequency sound penetration into, propagation within, and scattering from the shallow-water seafloor. One finding is that high-frequency acoustic penetration into sediments at grazing angles below the critical angle is possible--an important issue in detection of buried mines.

Dr. Thorsos is also presently leading a project to improve our understanding of the effects of sea surface and bottom roughness on shallow water propagation, and to determine the best approaches to modeling this propagation. A specialist in numerical studies of scattering theory and on the validity of scattering theory approximations, Dr. Thorsos publishes in the Journal of the Acoustical Society of America and the IEEE Journal of Oceanic Engineering.

Department Affiliation



B.S. Physics, Harvey Mudd College, 1965

M.S. Engineering & Applied Science, University of California, Davis-Livermore, 1966

Ph.D. Theoretical Nuclear Physics, MIT, 1972


2000-present and while at APL-UW

Subsurface acoustic ducts in the Northern California current system

Xu, G., R.R. Harcourt, D. Tang, B.T. Hefner, E.I. Thorsos, and J.B. Mickett, "Subsurface acoustic ducts in the Northern California current system," J. Acoust. Soc. Am., 155, 1881-1894, doi:10.1121/10.0024146, 2024.

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7 Mar 2024

This study investigates the subsurface sound channel or acoustic duct that appears seasonally along the U.S. Pacific Northwest coast below the surface mixed layer. The duct has a significant impact on sound propagation at mid-frequencies by trapping sound energy and reducing transmission loss within the channel. A survey of the sound-speed profiles obtained from archived mooring and glider observations reveals that the duct is more prevalent in summer to fall than in winter to spring and offshore of the shelf break than over the shelf. The occurrence of the subsurface duct is typically associated with the presence of a strong halocline and a reduced thermocline or temperature inversion. Furthermore, the duct observed over the shelf slope corresponds to a vertically sheared along-slope velocity profile, characterized by equatorward near-surface flow overlaying poleward subsurface flow. Two potential duct formation mechanisms are examined in this study, which are seasonal surface heat exchange and baroclinic advection of distinct water masses. The former mechanism regulates the formation of a downward-refracting sound-speed gradient that caps the duct near the sea surface, while the latter contributes to the formation of an upward-refracting sound-speed gradient that defines the duct's lower boundary.

Open ocean ambient noise data in the frequency band of 100 Hz – 50 kHz from the Pacific Ocean

Yang, J., J.A. Nystuen, S.C. Riser, and E.I. Thorsos, "Open ocean ambient noise data in the frequency band of 100 Hz – 50 kHz from the Pacific Ocean," JASA Express Lett., 3, doi:10.1121/10.0017349, 2023.

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1 Mar 2023

Bubbles from wind generated breaking surface waves are the dominant ambient noise source. With ambient noise data collected in the open ocean between 100 Hz and 50 kHz from 1999 to 2022, the ambient noise level is observed to sharply decrease as wind speed increases beyond 15 m/s for frequencies higher than 4 kHz. Data-model comparisons show a mismatch, as existing models including the Wenz curves are monotonic in nature. The decrease at high wind speeds and frequencies is likely due to attenuation when ambient sound propagates through the deeper and denser bubble layer for high sea conditions.

Macroscopic observations of diel fish movements around a shallow water artificial reef using a mid-frequency horizontal-looking sonar

Lee, W.-J., D. Tang, T.K. Stanton, and E.I. Thorsos, "Macroscopic observations of diel fish movements around a shallow water artificial reef using a mid-frequency horizontal-looking sonar," J. Acoust. Soc. Am., 144, 1424-1434, doi:10.1121/1.5054013, 2018.

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18 Sep 2018

The twilight feeding migration of fish around a shallow water artificial reef (a shipwreck) was observed by a horizontal-looking, mid-frequency sonar. The sonar operated at frequencies between 1.8 and 3.6 kHz and consisted of a co-located source and horizontal line array deployed at 4 km from the reef. The experiment was conducted in a well-mixed shallow water waveguide which is conducive to characterizing fish aggregations at these distances. Large aggregations of fish were repeatedly seen to emerge rapidly from the shipwreck at dusk, disperse into the surrounding area during the night, and quickly converge back to the shipwreck at dawn. This is a rare, macroscopic observation of an ecologically-important reef fish behavior, delivered at the level of aggregations, instead of individual fish tracks that have been documented previously. The significance of this observation on sonar performance associated with target detection in the presence of fish clutter is discussed based on analyses of echo intensity and statistics. Building on previous studies of long-range fish echoes, this study further substantiates the unique utility of such sonar systems as an ecosystem monitoring tool, and illustrates the importance of considering the impact of the presence of fish on sonar applications.

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