And just sticking to counting, a not exceptionally well-trained ear could already count how many letters you typed and if you pressed backspace (at least with the double-width backspace, sound is definitely different)
> When trained on keystrokes recorded by a nearby phone, the classifier achieved an accuracy of 95%, the highest accuracy seen without the use of a language model. When trained on keystrokes recorded using the video-conferencing software Zoom, an accuracy of 93% was achieved, a new best for the medium.