What do you mean by microphone?

Is audio analysis of keyboard chatter a thing or are we leaking passwords when we verbally communicate them to a co-worker?

I don't think this is related, but I found this keylogging technique combining microphone, camera, accelerometer data to approximate finger/thumb positions for PIN numbers: http://www.cl.cam.ac.uk/~rja14/Papers/pinskimmer_spsm13.pdf