Research Summaries

Back 32-Channel Digitizer for a Moored Hydrophone Array in Low-to-Mid Frequency Shallow-Water Acoustics Experiments

Fiscal Year 2011
Division Graduate School of Engineering & Applied Science
Department Oceanography
Investigator(s) Chiu, Ching-Sang
Sponsor Office of Naval Research (Navy)
Summary The purchase of an in situ, 32-channel digitizer capable of sampling at a rate of 8 kHz, with a maximum depth rating of 1 km and a data storage capacity sufficient to support continuous recording for a 10-day period, is proposed. The proposed digitizer is designed to connect to moored receiver array that is in the proposer's equipment inventory. This existing array has 32 equally spaced hydrophones forming an acoustic aperture of 155 m. The combined digitizer and array system will enable the measurement of the horizontal or vertical properties (depending on the moored orientation) of the low-to-mid frequency shallow-water sound field. Particularly, when the array is moored horizontally on the bottom, the proposed digitizer will enable un-aliased measurements of the horizontal coherences of both signal and noise in the upper-low to mid frequency (500-3,000 Hz) band and the horizontal directionality of noise in the 10-150 Hz band. When the array is moored vertically, the digitizer will enable the measurements of the depth structure of the low-to-mid frequency signal and noise fields including decompositions into modes and rays. At present, there are only two moored 32-channel receiver arrays available to the basic research community, namely the Applied Research Laboratory, University of Texas at Austin (ARL-UT) SWAMI-32 array and the Woods Hole Oceanographic Institution (WHOI) SHARK array. The proposal equipment will complement those two arrays with added diversities in the frequency and angular regimes as well as added horizontal coverage. Increased horizontal coverage is particularly important to support future research to investigate three-dimensional effects on sound propagation caused by a sharp front, large amplitude internal waves and significant bathymetric changes, which are common environmental features in a shelf-slope environment. The first deployment of the proposed equipment will be in the next multi-institutional shallow-water acoustics experiment that is targeted for the FY12-12 timeframe.
Keywords Ocean Acoustics, Battlespace Environment
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Data Publications, theses (not shown) and data repositories will be added to the portal record when information is available in FAIRS and brought back to the portal