Now, this is a very interesting bug. Under specific and reproducable circumstances the STO Client plays the audio part of an mpeg file in the background after selecting a character and its loaded into the game. The audio volume is changeable through the games master volume. I believe this is not only the clients fault but the whole directx pipeline comes to play here.
I run Win7 64bit, AMD HD7850 with the 14.10 drivers, current stable VLC version on directx renderer.
How it works: Play a video file (unsure if exclusive to but with mp3 or mp4a coded audio) with VLC, pause the video and start the client through ARC. When the game loads(the first loading screen appears), VLC crashes(its a known bug with the directx renderer), the game goes to character select and you select one. When you enter the zone the audio starts playing in the background. The volume is only low but noticeable STO uses automatic renderer. The kicker is that it plays exactly the audio from the video file that just crashed in VLC.
My guess is that somehow during the VLC crash the video isnt fully unloaded so the driver thinks both things are running.
If the devs need any more info I am happy to provide.