I lose audio of all game sounds when accepting a party invitation to play in WvW. Even if I have audio through my headset when I first log in, the game noises are completely lost after I enter WvW. This seems consistent with any WvW region, though I have not tested them all.
My headphones are functional, as I can hear my party members through teamspeak.
Audio is still lost when I return to PvE, however, the reason I know this must be a bug is if I fully log out and relaunch GW2, the audio returns with all the same settings in the audio panel as before playing WvW with a party; the game is not somehow muted accidentally.
MacBook Pro, Mid 2012
Processor 2.7 GHz Intel Core i7
Memory 8 GB 1600 MHz DDR3
Graphics NVIDIA GeForce GT 650M 1024 MB
Software OS X 10.8.5 (12F2501)