Estimating the Acoustic Modal Arrivals Using Signals Transmitted from Two Sound Sources to a Vertical Line Hydrophone Array in the 1996 Shelfbreak Primer Experiment

摘要

During the 1996 multi-institutional Shelfbreak PRIMER experiment, low frequency sound sources were moored on the continental slope south of Cape Cod. These sources transmitted phase encoded tomography signals which were monitored by vertical-line hydrophone arrays moored on the continental shelf. The measured signals were processed for the acoustic modal arrivals and their variability in time. The processing entailed pulse compression, coherent averaging, local sound-speed profile updates and an application of the Chiu-Miller-Lynch model- based modal beamforming technique. Th this thesis, the signal processing procedure is discussed and the modal arrival estimates are examined. The model- based estimates are found to be of high quality, with all propagating modes individually resolved. This unambiguous separation of the high modes cannot be achieved using simple least-squares techniques because of under sampling. The temporal variability of the modal amplitudes and travel times are found to be related to ocean processes that are unique to the shelf-slope littoral environment.