Quantifying seabed and other environmental information contained in ocean ambient noise

The ocean ambient noise field contains a surprising amount of information about the environment. Information about the seabed includes, layering structure, sound speed, density, and attenuation. There is also information about the ocean environment such as water column sound speed, volume attenuation, and the sea-state. Estimators for these quantities have been developed based mostly on vertical hydrophone arrays and beamforming. Although this has led to some simple and direct estimates for important quantities such as bottom loss, these estimates may be less than ideal in some cases. For example, when using inadequately sampled arrays or in certain unfavorable measurement geometries. The Fisher information can be used to quantify the basic information available in the noise measurements; and its inverse, the Cramer-Rao lower bound (CRLB), provides the lower limit on the variance of any unbiased estimator. The CRLB can be used to study the feasibility of various measurement configurations and parameter se...