I have exactly the same issue and rebooting temporarily restarts the sounds as normal.
I found and quit the coreaudiod file. It apparently fixed the sound issue.
I am a serious amateur with dangerous flyin' fingers so I should stop tinkering and ask if the coreaudiod file needs some kind of restarting or will simply closing the Activity monitor window be all that is needed?
A one-time force sleep foloowed by re-waking didn't make the sound problem reappear. I guess that's progress.
Thanks for the suggestions. (I wish I knew what the heck I was doing.)
;-)
--GG