UC San Diego

This presentation describes a demonstration of ambient acoustic noise processing on a set of free floating oceanic receivers whose relative positions vary with time. We show that we are able to retrieve information that is relevant to the travel time between the receivers. With thousands of short time cross-correlations of varying distance, we show that on average, the decrease in amplitude of the noise correlation function with increased separation follows a power law. This suggests that there may be amplitude information that is embedded in the noise correlation function. We develop an incoherent beamformer, which shows that it is possible to determine a source direction using an array with moving elements and large element separation. We show how the noise correlation function varies in the presence of a boat with a known GPS trajectory, and how this information can be used recover the relative geometry of the deformable array. This work indicates that the relative geometry of an array can be estimated using only passive signals and the automatic identification system already present in many coastal communities.