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Wu-Jung Lee Research Associate wjlee@apl.washington.edu Phone 206-685-3904 |
Biosketch
I am interested in the use of sound by both human and animals to observe and understand the environment. My research spans two primary areas: acoustical oceanography, where I develop and apply active acoustic sensing techniques to infer properties of the ocean interior; and animal echolocation, where I combine experimental and computational approaches to understand the closed-loop sensorimotor feedback in echolocating bats and dolphins. In both areas, I focus on two fundamental aspects for achieving high confidence active acoustic sensing: 1) sampling what can we do to collect better information? and 2) inference how do we make reliable interpretation of echo information? Under these overarching themes, I am working to expand acoustic sensing capability for marine ecosystem monitoring at large temporal and spatial scales, and use echolocating animals as biological models to inspire adaptive sampling strategies in an active acoustic context.
Education
B.S. Electrical Engineering and Life Sciences, National Taiwan University, 2005
Ph.D. Oceanographic Engineering, Massachusetts Institution of Technology/Woods Hole Oceanographic Institution Joint Program in Applied Ocean Physics and Engineer, 2013
Publications |
2000-present and while at APL-UW |
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Echo statistics associated with discrete scatterers: A tutorial on physics-based methods Stanton, T.K., W.-J. Lee, and K. Baik, "Echo statistics associated with discrete scatterers: A tutorial on physics-based methods," J. Acoust. Soc. Am., 144, doi:10.1121/1.5052255, 2018. |
More Info |
6 Dec 2018 ![]() |
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When a beam emitted from an active monostatic sensor system sweeps across a volume, the echoes from scatterers present will fluctuate from ping to ping due to various interference phenomena and statistical processes. Observations of these fluctuations can be used, in combination with models, to infer properties of the scatterers such as numerical density. Modeling the fluctuations can also help predict system performance and associated uncertainties in expected echoes. This tutorial focuses on "physics-based statistics," which is a predictive form of modeling the fluctuations. The modeling is based principally on the physics of the scattering by individual scatterers, addition of echoes from randomized multiple scatterers, system effects involving the beampattern and signal type, and signal theory including matched filter processing. Some consideration is also given to environment-specific effects such as the presence of boundaries and heterogeneities in the medium. Although the modeling was inspired by applications of sonar in the field of underwater acoustics, the material is presented in a general form, and involving only scalar fields. Therefore, it is broadly applicable to other areas such as medical ultrasound, non-destructive acoustic testing, in-air acoustics, as well as radar and lasers. |
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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 ![]() |
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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. |
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Tongue-driven sonar beam steering by a lingual-echolocating fruit bat Lee, W.-J., B. Falk, C. Chiu, A. Krishnan, J.H. Arbour, C.F. Moss, "Tongue-driven sonar beam steering by a lingual-echolocating fruit bat," Plos Biol., 15, e2003148, doi:10.1371/journal.pbio.2003148, 2017. |
More Info |
15 Dec 2017 ![]() |
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Animals enhance sensory acquisition from a specific direction by movements of head, ears or eyes. As active sensing animals, echolocating bats also aim their directional sonar beam to selectively "illuminate" a confined volume of space, facilitating efficient information processing by reducing echo interference and clutter. Such sonar beam control is generally achieved by head movements or shape changes of the sound-emitting mouth or nose. However, lingual-echolocating Egyptian fruit bats, Rousettus aegyptiacus, which produce sound by clicking their tongue, can dramatically change beam direction at very short temporal intervals without visible morphological changes. The mechanism supporting this capability has remained a mystery. |
In The News
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Scientists unravel the ocean's mysteries with cloud computing UW Information Technology, Elizabeth Sharpe The OOI Cabled Array is delivering data on a scale that was previously not possible. More than 140 instruments are working simultaneously. |
8 Nov 2018
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Fruit bat's locating clicks echo sophisticated radar Reuters, Jim Drury Researchers at university in the United States have discovered a sophisticated form of echolocation in bats, one that is remarkably similar to human-made location systems. |
22 Apr 2018
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Navigating with the tongue, the Egyptian fruit bat way! Research Matters, Jigu This study presents the first evidence that the direction of sonar beam can be changed by moving the tongue, which causes changes in phase difference across a series of sound sources located along the side of the bat’s mouth. |
3 Apr 2018
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