title: Green's function retrieval through cross-correlations in a two-dimensional complex reverberating medium.
abstract: Cross-correlations of ambient noise averaged at two receivers lead to the reconstruction of the two-point Green's function, provided that the wave-field is uniform azimuthally, and also temporally and spatially uncorrelated. This condition depends on the spatial distribution of the sources and the presence of heterogeneities that act as uncorrelated secondary sources. This study aims to evaluate the relative contributions of source distribution and medium complexity in the two-point cross-correlations by means of numerical simulations and laboratory experiments in a finite-size reverberant two-dimensional (2D) plate. The experiments show that the fit between the cross-correlation and the 2D Green's function depends strongly on the nature of the source used to excite the plate. A turbulent air-jet produces a spatially uncorrelated acoustic field that rapidly builds up the Green's function. On the other hand, extracting the Green's function from cross-correlations of point-like sources requires more realizations and long recordings to balance the effect of the most energetic first arrivals. When the Green's function involves other arrivals than the direct wave, numerical simulations confirm the better Green's function reconstruction with a spatially uniform source distribution than the typical contour-like source distribution surrounding the receivers that systematically gives rise to spurious phases.
authors.affiliation: ISTerre, Université Joseph Fourier, Grenoble, BP 53 38041 Grenoble CEDEX 9, France.
authors.forename: Andrea
authors.initials: A
authors.lastname: Colombi
authors.affiliation: ISTEP, Institut des Sciences de la Terre de Paris, UPMC, Universit Pierre et Marie Curie, 4 place Jussieu F-75005, Paris, France.
authors.forename: Lapo
authors.initials: L
authors.lastname: Boschi
authors.affiliation: ISTerre, Université Joseph Fourier, Grenoble, BP 53 38041 Grenoble CEDEX 9, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Roux
authors.affiliation: ISTerre, Université Joseph Fourier, Grenoble, BP 53 38041 Grenoble CEDEX 9, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Campillo
mesh_terms: D000162:Acoustics; D003198:Computer Simulation; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014732:Vibration