I updated to 13.04 yesterday by changing repositories from Quantal to Raring and subsequently certain applications yield no sound. Web apps (youtube, Netflix, etc) and rhythmbox all have sound, but the master volume control (both in settings and using the volume wheel on my keyboards) does not respond. Also, video games being run through stream do no have sound. A little light googling yielded a bug report that described roughly the same thing, but I haven't found anything regarding a fix, so I wanted to post something here and see if anyone's gotten anywhere.