We get a sound file on which we can hear someone typing a text on a keyboard.
I have used [this acoustic keylogger from Github](https://github.com/shoyo/acoustic-keylogger) to detect the keystrokes and extract features from them.
This allows me to group similar keystrokes, so I only get 25 different types.Thus I have a monoaplhabetic substitution of the typed text, which I decrypt with [dcode](https://www.dcode.fr/monoalphabetic-substitution).
See original writeup for detailed instructions.