[chrismorgan]

The space bar is just a big obvious form of audio attack that even humans can do with no tools or training, but really, if an attacker can hear you typing the password, it’s very heavily at risk. You can infer much more purely from the sound about the positioning of the hand and likely finger movements: in timing, most simply, but also in how sound bounces differently from different parts of the keyboard depending on what else is around (including the hands), and more. Practical attacks of this kind have been demonstrated.

It is thus a security Best Practice for streamers and the likes to mute their microphones while typing passwords.

Really, all senses leak information like this. Wifi signals are enough to see round corners and steal passwords. Even wearing a sleeveless shirt and having your upper arms visible to a camera leaks a little information from the small arm and theoretically even muscle movements.