There was a similar story a couple of years before, where they did almost the same with vibrations on other objects https://arstechnica.com/science/2014/08/researchers-reconstruct-human-speech-by-recording-a-potato-chip-bag/
For those who find this interesting: over the last few years there has been some very interesting security research on these advanced exfiltration techniques. Here’s an example with fax:
Here’s another one from the same school as the original article:
I’ve often wondered if high-powered telescopes could see places in a room out of the line of sight by focusing on an internal reflection at a boundary between crystals within a glass windowpane.
Continues to show that metadata just takes a while longer, but you still get the data eventually.