Have you double checked that all of your in-game audio options are set correctly. Press escape while in-game and click on 'Sound.' In there, make sure that the sliders for the announcer and music are turned up and neither of them are muted. If you make any changes, be sure to click ok, if you don't the settings won't be saved.
If this all seems correct, let us know, and if anyone else if have a problem with music or the announcer, please give us a heads up in this thread.