I think there's no exact separate voice sound available, I wish there was too...
There seems to be only "sound" and "music" options, and "sound" covers the game sound effects (shooting, explosions, ding, announcer, etc) and voice (mic), as music just covers the intro song and music that you'd come across in custom maps.
If you want to listen to music, I recommend to have it playing somewhere besides your computer through your headphones, like a stereo sitting by you or something