It was suggested I post this here in the Game Bugs sub-forum, as well, so here goes:
I’m not sure if this belongs here or over in Game Bugs, but…
While doing one of the Living Story instances (I’ve done it [World Summit] a few times before) today, when minimizing Guild Wars 2, I can still hear the music and other audio effects of the game. This didn’t happen before today, so I’m guessing it was caused by the patch.
Edit: I’ve noticed the mute in background option works outside of that instance.