Don’t worry, though. Facebook says they’re respecting your privacy while they do this. While ambient audio is definitely being recorded, they’re not storing exactly what the microphone picks up. The new feature works just like Shazam does: it tries to match an audio fingerprint from your environment with one in its database. The goal is to figure out if you’re listening to particular song or watching a TV show like The Simpsons.
Source: Facebook app now listens and records audio when you post updates from your phone – Geek.com