The dataminers have been at it again, revealing some more sound files from the upcoming patch 5.1. These ones are PvP-specific, announcing key events in arenas and battlegrounds. If you listen to the sound files (in a video after the break), you can hear that it's things like "The arena battle is about to begin" or "the gate of the yellow moon was destroyed". They're read in a male or female voice, which varies between sounding excitable and indifferent!
Now, I usually do my very best to approach new features with a positive viewpoint at best, and an open mind at worst, but I really hope these come with the option to turn them off. I'm fairly confident that they will, but not 100% sure.