Tomographic & Geophysical Inversions from Opportunistic Sound Sources

Abstract : The fundamental goal is to develop an advanced passive acoustic monitoring system that can be used to characterize ocean acoustic phenomena in ocean regions that are currently too isolated or remote to justify expensive exploratory research, and to provide cost-effective means to conduct field research into advanced coherent beamforming and geoacoustic inversion,methods The work also seeks to stimulate the further development of low-cost, low-power, autonomous acoustic recorders, by demonstrating how passive acoustic time-synchronization techniques can effectively convert a set of these recorders into a coherent beamforming array. The objectives are to develop and demonstrate modular passive acoustic systems for studies in three-dimensional acoustic tracking and geoacoustic inversion, by exploiting advances in low-power recording technology, and by using knowledge of ambient noise spatial structure to time-align independent recorder records without the need for active timing sources. Connecting single-channel recorders with rope and/or fishing gear can create a modular instarray that can be arranged with variable aperture, hydrophone spacing, and orientation. This array system is easy to transport and deploy in less-than-ideal circumstances. These systems can be used to perform acoustic inversion and tracking studies using opportunistic sounds such as marine mammal vocalizations.