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Ocean Acoustic Waveguide Remote Sensing (OAWRS). Helen Dickson. Review: Active Acoustic Sensing. An acoustic signal is generated Sound waves travel through the water and scatter off objects Backscattered sound is recorded. Review: Conventional Fish Finding Sonar (CFFS).
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Ocean Acoustic Waveguide Remote Sensing(OAWRS) Helen Dickson
Review: Active Acoustic Sensing • An acoustic signal is generated • Sound waves travel through the water and scatter off objects • Backscattered sound is recorded
Review: Conventional Fish Finding Sonar (CFFS) • Uses active acoustic sensing • Sends sound waves straight down through the water column
Problems of Conventional Fish Finding Sonar • Attenuation • Frequency • Image size • Sampling frequency
Ocean Acoustic Waveguide Remote Sensing • Method of active acoustic sensing • Developed by MIT • Sends sound waves horizontally through the water column
Acoustic Waveguides • Physical structures for guiding waves • Allow acoustic waves to travel long distances with little attenuation • The continental shelf as a waveguide
Ocean Acoustic Waveguide Remote Sensing • Little attenuation • Lower frequency • Much larger image (1,000s of square km’s) • Images created every minute (or less)
Applications • Shoal Characteristics: • Formation (critical density) • Migration • Leaders • Monitor and conserve fish populations • Identify fish species based on return signal
Applications • Acoustic clutter • Acoustic returns from objects in the water other than the intended target • Is it a submarine or is it a school of fish? • Important in Navy operations • OAWRS allows more detailed information to be gathered
References • Holden, Constance. Sound Sightings. 2006. Science. 313(5788):777 • Makris, Nicholas C., et al. Fish Population and Behavior Revealed by Instantaneous Continental Shelf-Scale Imaging. 2006. Science. 311(5761):660-663. • Makris, Nicholas C. et al. Critical Population Density Triggers Rapid Formation of Vast Oceanic Fish Shoals. 2009. Science. 323(5922):1734-1737. • Makris, Nicholas C. Acoustic Clutter and Ocean Acoustic Waveguide Remote Sensing (OAWRS) in Continental Shelf Environments. http://www.onr.navy.mil/sci_tech/32/reports/docs/08/oamakris.pdf • Makris, Nicholas C. Continuous Monitoring of Fish Population and Behavior by Instantaneous Continental-Shelf-Scale Imaging with Ocean Waveguide Acoustics. http://www.onr.navy.mil/sci_tech/32/reports/docs/08/npmakris.pdf • Ratilal, Purnima et al. Long range acoustic imaging of the continental shelf environment: The Acoustic Clutter Reconnaissance Experiment 2001. 2005. Journal of The Acoustic Society of America. 117(4):1977-1998. • Woods Hole Oceanographic Institution. 2007. http://www.whoi.edu/page.do?pid=10897&i=2041&x=131