Replying to Any computer people, I'm dumb

Ok so I can't hear audio when I'm streaming video. Whether it's embedded here, on youtube, whatever. I get no sound. It happened once before, then firefox updated itself and the problem went away. Now just the other day firefox updated again and the problem is back.

I've tried all the stuff on the youtube help page. I googled it, tried all that crap too. Nothing has changed in my firewall or anti virus settings and from what I can tell they are not blocking any third party flash stuff. I reinstalled Flash Player, updated Java, got squat.

What gives?