Time-reversal inside a granular suspension to probe ultrasound diffusion
We demonstrate that ultrasound diffusion—typically associated with the transport of average wave energy and the breaking of time-reversal symmetry—can nonetheless be revealed through a time-reversal experiment. This is achieved using an unprecedented configuration: A single piezoelectric transducer,...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | Uruguay |
| Institución: | Universidad de la República |
| Repositorio: | COLIBRI |
| Idioma: | inglés |
| OAI Identifier: | oai:colibri.udelar.edu.uy:20.500.12008/53923 |
| Acceso en línea: | https://hdl.handle.net/20.500.12008/53923 |
| Access Level: | acceso abierto |
| Palabra clave: | Acoustic wave phenomena Ballistic transport Diffusion Geometrical and wave optics Granular packing Mesoscopics Ultrasound attenuation Wave scattering Ultrasound techniques |
| Sumario: | We demonstrate that ultrasound diffusion—typically associated with the transport of average wave energy and the breaking of time-reversal symmetry—can nonetheless be revealed through a time-reversal experiment. This is achieved using an unprecedented configuration: A single piezoelectric transducer, acting as a time-reversal mirror (TRM), is buried deep inside a strongly scattering medium (a dense granular suspension), while an array of transducers is positioned at a distance, outside the scattering region. A short pulse is emitted by a single array element and the TRM records the resulting ultrasonic field, composed of a coherent ballistic wave followed by a diffuse coda wave. When the entire coda is time-reversed and re-emitted from the TRM, the wave refocuses at the original source with a focal spot size that decreases with the inverse of the TRM depth, consistent with diffusive transport. By time-reversing short coda segments at increasing times , we observe a focal spot size scaling as 1/√, where is the ultrasound diffusion coefficient. Fitting this evolution with a microscopic diffusion model allows us to extract . Remarkably, this measurement does not require ensemble averaging, because of the inherent stability of time-reversal against statistical fluctuations. |
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