We did this over 15 years ago without ai.

Link?

It's not 15 years ago but I remember this[0] being shared on HN 5 years ago. I can't find them at the moment but I also do remember seeing whitepapers outlining the same techniques before that.

This one is interesting to me, now, considering who the author is.

[0] https://github.com/ggerganov/kbd-audio