Echoes, sounds that are repeated or reverberate as a result of waves reflected back to the listener, occur in several physical systems. In physics research, echoes are typically used to eliminate the effects of dephasing caused by a system’s interactions with the environment, as well as to unveil the inherent properties of certain objects.
![](https://scx1.b-cdn.net/csz/news/tmb/2020/theexperimen.jpg)
Source:
https://phys.org/news/2020-02-experimental-echoes-molecule.html