Providence Section - 5:30 PM March 24
Since sound propagates in the water out to long distances, it is ideal for detecting and locating objects in the ocean and studying ocean properties. In passive sonar, sensors, typically arrays of hydrophones, “listen” to the noise radiated by the propulsions plants of ships and submarines. The signals can also include sounds emitted by marine mammals such as whales. Passive sonar signal processing steps include detection of the signal, classification of the type of the signal and its source, and determining its position in the ocean. Active sonar is similar to passive sonar, except that the sonar system now itself transmits acoustic energy into the water and detects objects by the acoustic energy that is reflected or backscattered from them, i.e. an echo. Uses of active sonar include the detection of submarines, mines, mapping and imaging of the seafloor, fish finding, and obstacle avoidance. Another application of sound in the ocean is acoustic tomography. Acoustic tomography is a technique for inferri ng properties of the ocean traversed by a sound field by measuring the changes caused to the acoustic signal by temperature variations, bottom structure, and currents, thus enabling rapid long range remote sensing of the ocean.
Alas, the underwater environment is highly challenging from the perspective of underwater acoustic signal processing. There are a myriad of unwanted manmade and natural noise sources to contend with such as machinery noise from commercial shipping and military vessels, breaking waves, rain, and biologics. In active sonar, the primary source of interference is reverberation from sound backscattered from the ocean bottom. These interferers have complicated spatial-temporal structures and can be highly non-stationary. Furthermore, the signals themselves are weak and have been distorted multipath propagation. In this talk I will describe passive and active sonar systems and give an overview of the challenges facing underwater signal processing and techniques used along with some actual synthetic aperture sonar examples.
Ivars P. Kirsteins received the Ph.D. in 1991 in electrical engineering from the University of Rhode Island and has had over 18 years of experience working on both active and passive sonar signal processing. Currently he is with the Naval Undersea Warfare Center in Newport, RI. From 1992 to 1995 he was senior scientist at the SACLANT Undersea Research Centre, La Spezia, Italy doing research on adaptive signal processing algorithms for active sonar. He has authored many articles on signal processing including adaptive interference cancellation, GLRT detectors, blind source separation, and high-resolution time delay estimation. Presently he is working on passive sonar techniques for adaptive detection and normalization and developing blind signal separation techniques to suppress interference in synthetic aperture sonar.
The meeting will be held
Wednesday March 24 at 5:30 PM at the University of Massachusetts Dartmouth Advance
Technology and Manufacturing Center (ATMC). Directions: Route I-195 east or west to the Route 24s exit
(number 8A) towards TIVERTON R.I./NEWPORT R.I. Take the BRAYTON AVE/EASTERN AVE exit
(number 2). Keep RIGHT at the fork in the ramp. Merge onto EASTERN AVE/BRAYTON AVE. Turn
RIGHT onto US-6/MARTINE ST. The ATMC is at 151 Martine Street, Fall River, in the South
Coast Research & Technology Park, approximately ¼ mile on the right.
Reservations are not required for the meeting, but encouraged. An optional, no host dinner with the speaker will take place after the talk, and be held at White’s of Westport (on US-6 approximately 1 mile east of the ATMC) starting at 7:00 PM. Reservations are required for the dinner. For reservations click link below or contact Howard Michel, e-mail: hmichel@umassd.edu, phone: (508) 910-6465.
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