title: Cross-correlations of diffuse noise in an ocean environment using eigenvalue based statistical inference.
abstract: Cross-correlations of diffuse noise fields can be used to extract environmental information. The influence of directional sources (usually ships) often results in a bias of the travel time estimates obtained from the cross-correlations. Using an array of sensors, insights from random matrix theory on the behavior of the eigenvalues of the sample covariance matrix (SCM) in an isotropic noise field are used to isolate the diffuse noise component from the directional sources. A sequential hypothesis testing of the eigenvalues of the SCM reveals eigenvalues dominated by loud sources that are statistical outliers for the assumed diffuse noise model. Travel times obtained from cross-correlations using only the diffuse noise component (i.e., by discarding or attenuating the outliers) converge to the predicted travel times based on the known array sensor spacing and measured sound speed at the site and are stable temporally (i.e., unbiased estimates). Data from the Shallow Water 2006 experiment demonstrates the effectiveness of this approach and that the signal-to-noise ratio builds up as the square root of time, as predicted by theory.
authors.affiliation: Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0238, USA. rmenon@ucsd.edu
authors.forename: Ravishankar
authors.initials: R
authors.lastname: Menon
authors.forename: Peter
authors.initials: P
authors.lastname: Gerstoft
authors.forename: William S
authors.initials: WS
authors.lastname: Hodgkiss
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D004058:Diffusion; D004784:Environmental Monitoring / Q000379:methods*; D005583:Fourier Analysis; D016014:Linear Models; D015233:Models, Statistical; D009038:Motion; D009622:Noise; D009792:Oceans and Seas; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers; D014867:Water
chemical_list: D014867:Water