Department of Mechanical Engineering
University of Michigan
2:00 - 2:30pm Beverages & Refreshments
2:30 - 4:00pm Seminar
Arrays of acoustic transducers are used for a wide variety of reconnaissance, surveillance, and remote sensing applications in the ocean. Array signal processing techniques are commonly used to determine the direction toward, or the location of, a remote unknown acoustic source or scatterer, and the necessary array signal processing is completed using recorded acoustic-field information at the frequencies of the received signal. Unfortunately, even at high signal-to-noise ratios, conventional remote sensing techniques have limitations set by the recorded frequencies, the spacing of the array elements, the geometrical extent of the array, and mismatch between the recorded and modeled acoustic fields. Interestingly, these limitations can be overcome through reliance on nonlinear acoustic-field products (aka autoproducts) that are constructed from in-the-signal-band field recordings. When sufficient signal bandwidth is available, the autoproducts can mimic out-of-the-signal-band acoustic fields. In this presentation, out-of-band field construction from in-band fields is illustrated using simulations and experimental measurements in a Lloyd’s mirror acoustic environment. In addition, unique remote sensing results based on such out-of-band information are compared to equivalent results from conventional in-band techniques using propagation simulations and measurements made in free-space and multipath ocean environments where scattering and/or array sparseness degrades the utility of the conventional techniques. [Sponsors: ONR, NAVSEA, and NSF].
David R. Dowling completed his doctorate in 1988 at Graduate Aeronautical Laboratories of the California Institute of Technology and moved north to Seattle to accommodate his wife's career in medicine. While there, he worked for a year in the Laser Technology Section of Boeing Aerospace, and then for almost three years as a post-doc at the Applied Physics Laboratory of the University of Washington. In 1992, he accepted a faculty position at the University of Michigan. Prof. Dowling is currently conducting research in acoustics and fluid mechanics. He teaches courses in these subjects and in experimental techniques. He is a fellow of the Acoustical Society of America, the American Society of Mechanical Engineers, and the American Physical Society – Division of Fluid Dynamics.
Hosted by: Asst. Prof. S.A. Mäkiharju, 6179 Etcheverry Hall (firstname.lastname@example.org)