World of Warcraft sound issue

I've had a sound issue with World of Warcraft for quite some time which was apparently made worse by the latest patch. Oftentimes, if something is right in front of my character, I can't hear it. If I'm fighting an enemy, I often need to turn my character slightly sideways to hear it. In the past, if I tried to have my character tell a joke, it was barely audible. Now when I try, it's completely silent. It also doesn't make any noise when I mount or dismount (though apparently if I take damage from a fall while mounted, I do hear it loud and clear). I've tolerated it until now, but having my character dead silent? That's going to get annoying fast. Anyone have any clue what could cause this?