Retrieving the scattering strength using noise correlation in a reverberant medium

TL;DR

This paper demonstrates how ambient-noise interferometry can be used to estimate the scattering strength of a scatterer in a reverberant medium by analyzing the decay of Green's function similarity over time.

Contribution

It introduces a novel formula linking Green's function decay to scattering strength and validates it experimentally in a reverberant plate.

Findings

Green's function similarity decays exponentially over time.

The proposed formula accurately estimates scattering strength.

Experimental validation confirms the method's reliability.

Abstract

We explore how ambient-noise interferometry can serve to track variations in the distribution of scatterers within a medium. Experiments are conducted in the presence and absence of a single scatterer that can occupy different positions within the propagation medium. We calculate the similarity between the Green's functions obtained in these cases (i.e., with versus without the scatterer) as a measure of the temporal variations in the Green's function, which shows exponential decay with respect to time. We also develop a formula that relates this decay to the scattering strength of the scatterer. The formulae are experimentally validated using experiments in a strongly reverberating duralumin plate. This proposed method for finding the scattering strength of the scatterer is based on information carried by the coda of the multiple echo arrivals. We confirm the reliability of this approach through a conventional method for the measurement of the scattering strength that is based on direct arrivals.