[jloughry]

That hardware capability is exploited in the following paper, if you want to know the details:

Mordechai Guri et al. (2016) 'SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit'.

http://cyber.bgu.ac.il/advanced-cyber/system/files/SPEAKE(a)...

By Mordechai Guri, Yosef Solewicz, Andrey Daidakulov, and Yuval Elovici.

[Sephr]

I'm getting access denied on that link. Do you have a mirror?

[antoinealb]

I was able to read it on Arxiv: https://arxiv.org/pdf/1611.07350.pdf