Had recently upgraded my copy of starcraft two so I could finally play through the protross campaign, as soon as I completed the third mission for ulnar the audio started to play the home screen music, no longer playing any appropriate sounds or music, no audio plays during any dialogues.
Hey, Nodma! It sounds like the audio files may have been corrupted after the upgrade. Have you tried reinstalling the game to check and make sure?
If it persist after this, I would suggest to #bug-report this over to our team so they can take out whats going on with the audio.