Long range source localization from single hydrophone spectrograms

A source near the deep sound channel axis excites mode groups (or paths) th at involve both deep sound channel and boundary interacting propagation. Di spersion from a broadband source as measured on a single hydrophone can be used to estimate source range. Furthermore, modal group speeds have a funct ional transition when passing through purely refractive to boundary reflect ing phase speed regions which, under certain conditions, provides additiona l arrival structure to aid in source localization. This additional arrival structure is in the form of a focal region in a spectrogram. Indeed, differ ent data sets from the Acoustic Thermometry of the Ocean Climate (ATOC) Pro gram [ATOC Consortium, Science 281, 1327-1332 (1998)] show that localizatio n can be accomplished using this focal region and/or the overall dispersion properties as originally suggested fifty years ago [M. Ewing and J. L. Wor zel, Gee. Sec. Am., Memoir 27 (1948)]. (C) 2001 Acoustical Society of Ameri ca.