Effects of Environmental Variability on Long-Range Underwater Sound Propagation: Mode Processing of LOAPEX

摘要

This report summarizes PI's efforts under the Grant Number N00140810195 to accomplish two main objectives: 1) to further develop the theory of underwater sound propagation in realistic deep ocean environments with an emphasis on mode coupling; 2) to test this theory against measurements made during 2004 Long-Range Ocean Acoustic Propagation Experiment (LOAPEX). Significant progress has been made in the development of a theory of acoustic scattering in long-range deep ocean propagation, especially the scattering of sound near the sound channel axis. The LOAPEX data shows generally good agreement between observations and theory. Our understanding of the influence of the background sound speed structure on the resulting wave field fluctuations has been improved. Also some progress has been made on extending the existing theory to the environments with strong range dependence. In addition, a study of oceanic acoustic response to acidification has been made. Two papers have been published during this study. The first paper focuses on importance of energy conservation constraint in the mode filtering implementation. The second paper is a study of ambient noise level change in the ocean due to acidification. Also two papers devoted to the modal analysis of LOAPEX measurements and comparisons with developed theory and existing numerical models have been written. All the work has been presented at several Acoustical Society of America (ASA) meetings and North Pacific Acoustic Laboratory (NPAL) workshops.