3 ms·

I think the backspace key would be the best key to try to find a reference for. It is often pressed multiple times in a row and would allow for recognition of c

• brador 13y ago
  You could also get a sketch map of the keyboard from key press volume, louder means closer, find backspace, model phone position in relation to keyboard position, take it from there.
  • sigkill 13y ago
    And the spacebar key, when hit, sounds different than the other keys. I'm not good with onomatopoeia but normal keys generally go tack-tack-tack while the spacebar goes tchick-tchick-tchick. It's noticeably different. This could actually prove quite scary since if you know the length of the 'tack', you're basically doing stupidly simple linear cryptanalysis.