Locating a small change in a multiple scattering environment

This article presents an imaging technique to locate a weak perturbation in a multiple scattering environment. We derive a formula to predict the spatiotemporal decorrelation of diffuse coda waves induced by an extra scatterer. Locating this new defect is formulated as an inverse problem which is solved by a maximum likelihood approach. Using elastic waves in the 50-400 kHz frequency band, we recover the position of a millimetric hole drilled in a concrete sample with a precision of a few centimeter. Note that the size of the defect is comparable to the size of the myriads of heterogeneities constituting the sample. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3431269]