No sound notifications in hangouts on Ubuntu with Firefox ?

So I have been upset about not having any sound notifications on my Ubuntu box 14.04 ever since I reinstalled everything. So here is a note for the future me, or anyone who has the same issue. After hours of fiddling with Google settings, pavucontrol, etc. it finally came down to one of these two: enable the Google Talk Plugin to "Always Enable" (add-ons / Plugins page of Firefox) instead of "Ask" and install the ubuntu-restricted-extras package to allow mp3 playback in the browser. Not sure which one did the trick for me, but it did, so maybe it can help someone out there.