Acoustic mode coherence in the Arctic Ocean
Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1986 The dual issues of modal decomposition for tonal sound fields and the temporal coherence of the modal amplitudes...
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
1986
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/3756 2023-05-15T14:35:35+02:00 Acoustic mode coherence in the Arctic Ocean Polcari, John J. Arctic Ocean 1986-05 application/pdf https://hdl.handle.net/1912/3756 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/3756 doi:10.1575/1912/3756 doi:10.1575/1912/3756 Underwater acoustics Sound-waves Thesis 1986 ftwhoas https://doi.org/10.1575/1912/3756 2022-05-28T22:58:04Z Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1986 The dual issues of modal decomposition for tonal sound fields and the temporal coherence of the modal amplitudes are investigated for the case of the central Arctic sound channel at very low frequencies (15-80 Hz). A detailed study of the Arctic modal structure for these frequencies reveals the central role played by the strong Arctic surface duct. The performance of each of four different modal beamforming algorithms when applied to the vertical array deployed during the FRAM IV Arctic Acoustic Experiment is analyzed. A multiple beam (or decoupled beam) least squares processor produces the most acceptable results for Arctic conditions. The modal decomposition is sensitive to vertical array tilt caused by hydrodynamic drag; a technique for its estimation from the acoustie data is developed. Tonal data taken from both the horizontal and vertical arrays deployed during FRAM IV is analyzed. Horizontal array results confirm the modal amplitudes generated from vertical array data. The rough surface scattering from the ice canopy places an upper limit of 40 Hz on efficient surface duct propagation. Attenuation measurements for the first mode show excellent agreement with predictions made for ice scattering using the method of small perturbations and experimental ice statistics. The high levels of coherence observed (O.95 to 0.99) show that tonal signal propagation in the Arctic channel is essentially deterministic for time periods well in excess of one hour. The various modes may then be considered to maintain a constant phase relationship over time. Thesis Arctic Arctic Ocean Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Arctic Arctic Ocean Arctic Sound ENVELOPE(-108.852,-108.852,67.534,67.534) Woods Hole, MA |
institution |
Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
topic |
Underwater acoustics Sound-waves |
spellingShingle |
Underwater acoustics Sound-waves Polcari, John J. Acoustic mode coherence in the Arctic Ocean |
topic_facet |
Underwater acoustics Sound-waves |
description |
Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1986 The dual issues of modal decomposition for tonal sound fields and the temporal coherence of the modal amplitudes are investigated for the case of the central Arctic sound channel at very low frequencies (15-80 Hz). A detailed study of the Arctic modal structure for these frequencies reveals the central role played by the strong Arctic surface duct. The performance of each of four different modal beamforming algorithms when applied to the vertical array deployed during the FRAM IV Arctic Acoustic Experiment is analyzed. A multiple beam (or decoupled beam) least squares processor produces the most acceptable results for Arctic conditions. The modal decomposition is sensitive to vertical array tilt caused by hydrodynamic drag; a technique for its estimation from the acoustie data is developed. Tonal data taken from both the horizontal and vertical arrays deployed during FRAM IV is analyzed. Horizontal array results confirm the modal amplitudes generated from vertical array data. The rough surface scattering from the ice canopy places an upper limit of 40 Hz on efficient surface duct propagation. Attenuation measurements for the first mode show excellent agreement with predictions made for ice scattering using the method of small perturbations and experimental ice statistics. The high levels of coherence observed (O.95 to 0.99) show that tonal signal propagation in the Arctic channel is essentially deterministic for time periods well in excess of one hour. The various modes may then be considered to maintain a constant phase relationship over time. |
format |
Thesis |
author |
Polcari, John J. |
author_facet |
Polcari, John J. |
author_sort |
Polcari, John J. |
title |
Acoustic mode coherence in the Arctic Ocean |
title_short |
Acoustic mode coherence in the Arctic Ocean |
title_full |
Acoustic mode coherence in the Arctic Ocean |
title_fullStr |
Acoustic mode coherence in the Arctic Ocean |
title_full_unstemmed |
Acoustic mode coherence in the Arctic Ocean |
title_sort |
acoustic mode coherence in the arctic ocean |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
1986 |
url |
https://hdl.handle.net/1912/3756 |
op_coverage |
Arctic Ocean |
long_lat |
ENVELOPE(-108.852,-108.852,67.534,67.534) |
geographic |
Arctic Arctic Ocean Arctic Sound |
geographic_facet |
Arctic Arctic Ocean Arctic Sound |
genre |
Arctic Arctic Ocean |
genre_facet |
Arctic Arctic Ocean |
op_source |
doi:10.1575/1912/3756 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/3756 doi:10.1575/1912/3756 |
op_doi |
https://doi.org/10.1575/1912/3756 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766308381332602880 |