Anyone interested in this will likely enjoy Don't Skype & Type![1] where researchers decoded keystrokes from background audio of Skype conversations. The best part is source code is available[2]. I wonder how many people are applying this to Twitch streamers or YouTube videos (especially any Talks at Google videos) today?
1. http://spritz.math.unipd.it/projects/dst/ 2. https://github.com/SPRITZ-Research-Group/Skype-Type
I've been working on a similar tool: https://github.com/ggerganov/kbd-audio (see the 'keytap' tool). Not sure how well it works yet, as I have made tests only with my setup. There is a live page that anyone can experiment with.