Abbot Philip A.
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ArticleExperimental and numerical studies of sound propagation over a submarine canyon northeast of Taiwan(IEEE, 2015-01-09) Lin, Ying-Tsong ; Duda, Timothy F. ; Emerson, Chris ; Gawarkiewicz, Glen G. ; Newhall, Arthur E. ; Calder, Brian ; Lynch, James F. ; Abbot, Philip A. ; Yang, Yiing-Jang ; Jan, SenA study of sound propagation over a submarine canyon northeast of Taiwan was made using mobile acoustic sources during a joint ocean acoustic and physical oceanographic experiment in 2009. The acoustic signal levels (equivalently, transmission losses) are reported here, and numerical models of 3-D sound propagation are employed to explain the underlying physics. The data show a significant decrease in sound intensity as the source crossed over the canyon, and the numerical model provides a physical insight into this effect. In addition, the model also suggests that reflection from the canyon seabed causes 3-D sound focusing when the direction of propagation is along the canyon axis, which remains to be validated in a future experiment. Environmental uncertainties of water sound speed, bottom geoacoustic properties, and bathymetry are addressed, and the implications for sound propagation prediction in a complex submarine canyon environment are also discussed.
ArticleOn whether azimuthal isotropy and alongshelf translational invariance are present in low-frequency acoustic propagation along the New Jersey shelfbreak(Acoustical Society of America, 2012-02) Lynch, James F. ; Emerson, Chris ; Abbot, Philip A. ; Gawarkiewicz, Glen G. ; Newhall, Arthur E. ; Lin, Ying-Tsong ; Duda, Timothy F.To understand the issues associated with the presence (or lack) of azimuthal isotropy and horizontal (along isobath) invariance of low-frequency (center frequencies of 600 Hz and 900 Hz) acoustic propagation in a shelfbreak environment, a series of experiments were conducted under the Autonomous Wide-Aperture Cluster for Surveillance component of the Shallow Water 2006 experiment. Transmission loss data reported here were from two mobile acoustic sources executing (nearly) circular tracks transmitting to sonobuoy receivers in the circle centers, and from one 12.5 km alongshelf acoustic track. The circle radii were 7.5 km. Data are from September 8, 2006. Details of the acoustic and environmental measurements are presented. Simple analytic and computer models are used to assess the variability expected due to the ocean and seabed conditions encountered. A comparison of model results and data is made, which shows preliminary consistency between the data and the models, but also points towards further work that should be undertaken specifically in enlarging the range and frequency parameter space, and in looking at integrated transmission loss.
ArticleShallow Water ’06 : a joint acoustic propagation/nonlinear internal wave physics experiment(Oceanography Society, 2007-12) Tang, Dajun ; Moum, James N. ; Lynch, James F. ; Abbot, Philip A. ; Chapman, Ross ; Dahl, Peter H. ; Duda, Timothy F. ; Gawarkiewicz, Glen G. ; Glenn, Scott M. ; Goff, John A. ; Graber, Hans C. ; Kemp, John N. ; Maffei, Andrew R. ; Nash, Jonathan D. ; Newhall, Arthur E.Since the end of the Cold War, the US Navy has had an increasing interest in continental shelves and slopes as operational areas. To work in such areas requires a good understanding of ocean acoustics, coastal physical oceanography, and, in the modern era, autonomous underwater vehicle (AUV) operations.
Technical ReportAcoustics and oceanographic observations collected during the QPE Experiment by Research Vessels OR1, OR2 and OR3 in the East China Sea in the Summer of 2009(Woods Hole Oceanographic Institution, 2010-08) Newhall, Arthur E. ; Lynch, James F. ; Gawarkiewicz, Glen G. ; Duda, Timothy F. ; McPhee, Neil M. ; Bahr, Frank B. ; Marquette, Craig D. ; Lin, Ying-Tsong ; Jan, Sen ; Wang, Joe ; Chen, Chi-Fang ; Chiu, Linus Y. S. ; Yang, Yiing-Jang ; Wei, Ruey-Chang ; Emerson, Chris ; Morton, David ; Abbot, Ted ; Abbot, Philip A. ; Calder, Brian ; Mayer, Larry A. ; Lermusiaux, Pierre F. J.This document describes data, sensors, and other useful information pertaining to the ONR sponsored QPE field program to quantify, predict and exploit uncertainty in observations and prediction of sound propagation. This experiment was a joint operation between Taiwanese and U.S. researchers to measure and assess uncertainty of predictions of acoustic transmission loss and ambient noise, and to observe the physical oceanography and geology that are necessary to improve their predictability. This work was performed over the continental shelf and slope northeast of Taiwan at two sites: one that was a relatively flat, homogeneous shelf region and a more complex geological site just shoreward of the shelfbreak that was influenced by the proximity of the Kuroshio Current. Environmental moorings and ADCP moorings were deployed and a shipboard SeaSoar vehicle was used to measure environmental spatial structure. In addition, multiple bottom moored receivers and a horizontal hydrophone array were deployed to sample transmission loss from a mobile source and ambient noise. The acoustic sensors, environmental sensors, shipboard resources, and experiment design, and their data, are presented and described in this technical report.