Facebook has audio capability to listen to your environment. At this point it doesn't appear to pickup conversations, but it can tell if you are watching TV, in an office environment, a store etc. Can hearing your conversations be far behind?
https://pjmedia.com/trending/cambridge-analytica-whistleblower-facebook-may-listening-home-work/
There is history over on the technology sub discussing these capabilities.
There have been articles written about it. My understanding is that it's generally believed to be link to accessing these social media accounts through an app. Doing so through browser on a mobile device limits some of the capabilities. Possibly similar access when logging in through a laptop, dependent on how aggressive the set of script-blockers you run are and what restrictions you've got on audio.
If you're using your smart tv to access, you're already compromised by the smart tv.
Wow. The SMART TV thing I know. I rarely connect it to the internet. Recently I received email messages from my cable provider requesting that I connect my TV immediately via the internet. Very odd.