Coherent backscattering of ultrasound without a source

TL;DR

This paper demonstrates a novel method to observe coherent backscattering of ultrasound without a nearby source by using time correlation of diffuse fields and thermal phonons, achieving high spatial resolution.

Contribution

It introduces a new approach to observe coherent backscattering effects without an active source, using correlation techniques and thermal phonons.

Findings

Coherent backscattering effect recovered within an array of sources and a distant receiver.

High spatial resolution of the enhancement cone achieved.

Demonstrated observation of the effect using thermal phonons without active sources.

Abstract

Coherent backscattering is due to constructive interferences of reciprocal paths and leads to an enhancement of the intensity of a multiply scattered field near its source. To observe this enhancement an array of receivers is conventionally placed close to the source. Our approach here is different. In a first experiment, we recover the coherent backscattering effect (CBE) within an array of sources and a distant receiver using time correlation of diffuse fields. The enhancement cone has an excellent spatial resolution. The dynamics of the enhancement factor is studied in a second experiment using correlation of thermal phonons at the same ultrasonic frequencies, without any active source.