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dc.contributor.authorSperry, Brian J.  Concept link
dc.coverage.spatialMonterey, CA
dc.date.accessioned2012-11-15T19:09:44Z
dc.date.available2012-11-15T19:09:44Z
dc.date.issued1994-05
dc.identifier.urihttps://hdl.handle.net/1912/5553
dc.descriptionSubmitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution May 1994en_US
dc.description.abstractDuring the 1991 Heard Island Feasibility Test, a vertical hydrophone array deployed off Monterey, CA, recorded transmissions from a low-frequency acoustic source nearly 18,000 km away. By determining the modal structure of the received transmissions, it is possible to characterize the physics of such long range propagation. This thesis focuses on the determination of the modal, or vertical, structure of the signal. It was necessary to first develop a conditioning scheme to address several data quality issues, including very low signal levels (-15 dB SNR on a single channel), large transient spikes, and a limited set of operational channels. Very narrowband filtering was used to obtain a 25 dB increase in SNR. Doppler shifts for each transmission event were predicted from available parameters and were found to be within ±2 mHz of the measured shifts. The modal analysis employed two methods: comparing variations in signal energy with depth to the vertical extent of the modes, and fitting the data using a least squares modal decomposition. The least squares performance given a subsampled basis set of modes was studied and improved upon through the use of diagonal loading. Lack of array orientation data hindered the analysis, and least squares fitting was used to estimate the most likely orientation. The least squares analysis indicated the presence of modes at least up to mode 7, possibly higher. This is significant in that predictions prior to the experiment were that all but the lowest modes would be attenuated by boundary interactions along the path. Results from independent analyses of the same data also support the conclusion that the signal structure is quite complex.en_US
dc.description.sponsorshipFunding for this work was provided by the Department of Energy Grant #DE-FG02- 91ER61100 (Vertical Arrays for the Heard Island Acoustic Feasibility Experiment on Monitoring Global Warming), and the University of California - Scripps ATOC Agreement, P0#10037359.en_US
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen_US
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen_US
dc.relation.ispartofseriesWHOI Thesesen_US
dc.subjectModal analysisen_US
dc.subjectSignal processingen_US
dc.subjectFrequency responseen_US
dc.titleModal analysis of vertical array receptions for the Heard Island Feasibility Testen_US
dc.typeThesisen_US
dc.identifier.doi10.1575/1912/5553


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