Ambient Noise Interferometry for Passive Characterization of Dynamic Environments

Non-invasive, stealthy nature of passive remote sensing combined with its low cost make passive techniques a promising supplement or replacement of traditional active remote sensing techniques. Coherent processing of diffuse wave fields has a proven potential for remote sensing of stationary environments. The proposed research extends noise interferometry to characterization of dynamic environments. We will develop “acoustic daylight” and “radio wave daylight” techniques for retrieval of information about targets and their surroundings from the ambient acoustic noise and the background radio waves; and determine which environmental parameters and types of targets can be effectively monitored through ambient noise interferometry. During Phase I we propose to demonstrate experimentally the feasibility of passive acoustic measurements of sound speed and flow velocity in a moving fluid and to evaluate necessary noise averaging times and receiver network geometry for detection of targets and achieving desired accuracy of passive acoustic measurements of environmental parameters. In case of positive results of Phase I, the efforts of Phase I optional part and Phase II will be directed toward extension of the interferometric approach to ambient acoustic noise in the ocean and to electromagnetic ambient noise in the microwave band in the atmosphere as well as to optimization of the data acquisition geometry, frequency band, and data processing algorithms to improve accuracy of passive travel time measurements and sensitivity to weak, transient environmental perturbations.