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,...
Saved in:
| 主要作者: | |
|---|---|
| 其他作者: | , , , , |
| 格式: | article |
| 語言: | 英语 |
| 出版: |
2025
|
| 主題: | |
| 在線閱讀: | https://hdl.handle.net/20.500.12008/53923 |
| 標簽: |
沒有標簽, 成為第一個標記此記錄!
|
| 總結: | 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. |
|---|