Use phone speaker as microphone

Just curious whether a phone's speaker could be used to listen/record... could a piece of software monitor the signals generated?I remember using my earphones as a microphone once and just wondered if it could be possible that someone could do the same with the speaker on a smartphone to avoid needing microphone permissions...?

Just curious whether a phone's speaker could be used to listen/record... could a piece of software monitor the signals generated?

I remember using my earphones as a microphone once and just wondered if it could be possible that someone could do the same with the speaker on a smartphone to avoid needing microphone permissions...?

http://ift.tt/eA8V8J