Ocean tomography with acoustic daylight

Abstract

Ambient noise in the ocean provides acoustic illumination, which can be used, similarly to daylight in the atmosphere, to visualize objects and characterize the environment. It has been shown theoretically that deterministic travel times between any two points in a moving or motionless, inhomogeneous, time-independent medium can be retrieved from the cross-correlation function of diffuse acoustic noise recorded at the two points, without a detailed knowledge of the noise field's sources or properties. In this paper, techniques are developed to account for receiver motion and suppress contributions due to powerful transient localized noise sources, such as nearby shipping, in order to enhance noise diffusivity. The data-processing techniques are applied to ambient noise recordings of opportunity, which were obtained as a by-product of a long-range sound propagation experiment in the Pacific Ocean. The feasibility of passive ocean acoustic tomography with ambient noise recorded at two vertical line arrays is demonstrated successfully. © 2010 by the American Geophysical Union.