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Underwater Acoustics, Bubble Scattering, and Signal Processing
A Seminar with R. Lee Culver, Sr.
RSVP to Sheron Williams
The Graduate Program in Acoustics at Penn State is a unique interdisciplinary program that leads to the degrees Master of Science in Acoustics, Master of Engineering in Acoustics, and Doctor of Philosophy in Acoustics. It is centered on acoustics, which is a subject that touches many diverse disciplines and allows many options for professional careers. The Program maintains a strong liaison with the Penn State Applied Research Laboratory (ARL), which is a major separately funded research unit of the University that has extensive research and development activities related to underwater acoustics. I will summarize 25 years of research in underwater acoustics as a Research Associate at ARL, as well as teaching and supervising students in the Graduate Program in Acoustics. Projects involving radiated noise measurement, acoustic scattering from bubbly ship wakes, autonomous underwater vehicle design, and others will be highlighted.
In addition, I will present results of an investigation into the effects of nearby bubbles on the gain achieved using an underwater array of hydrophones. We know that coherent processing of signals from multiple hydrophones in an array offers improvements in angular resolution and signal-to-noise ratio. This is because when the array is steered in a particular direction, the signals arriving from that direction are added in phase, and any signals arriving from other directions are not. Array gain (AG) is a measure of how much the signal arriving from the steering direction is amplified relative to signals arriving from all other directions. Our interest was in the manner by which the AG of an acoustic array operating in water that contains air bubbles is affected by scattering from nearby bubbles. The effects of bubbles on acoustic attenuation and dispersion were considered separate from their effects on AG. Acoustic measurements made in bubbly water using the AB Wood tank at the Institute of Sound and Vibration Research (ISVR), University of Southampton, in June 2008 show that as bubble density increases, relative phase shifts in individual hydrophone signals increase and signal correlation among the hydrophones is reduced. A theory and numerical simulation linking bubble density at the hydrophone to the AG is in good agreement with the measurements up to the point where multiple scattering becomes important.
R. Lee Culver is Senior Research Associate and Associate Professor of Acoustics at the Applied Research Laboratory of The Pennsylvania State University in State College, Pennsylvania. His research has focused on underwater acoustics and signal processing with application to Naval active and passive sonar systems. He has contributed to the development and evaluation of sonar systems for submarines, surface ships and torpedoes. In 2013 he received a Letter of Appreciation from the Department of the Navy PEO IWS 5.0 Undersea Systems. A member of the faculty of Penn State’s Graduate Program in Acoustics, he has taught classes in sonar signal processing, acoustical oceanography, and computational ocean acoustics, as well as supervised the theses of more than 30 MS and PhD students. He is a Fellow of the Acoustical Society of America and past Chairman of the Signal Processing Technical Committee. He is a member of IEEE and an Associate Editor for the IEEE Journal of Oceanic Engineering.