Volume mixer doesn't detect any sound

So you know how when you go to volume mixer and you see the green sound bar move yeah well no matter what Chrome, VLC or even a game NOTHING happens. it plays no sound so I can't watch Youtube or listen to music. I have windows 7 Black Edition and NEED to catch up on some Youtube channels plz halp (my computer has a built in speaker but even headphones and aux speakers don't work)