My iphone does not want to sound?

So I'm trying to listen to a video on YouTube and it does not make any noise so I use the buttons to turn it up and no bars show up. I checked the settings and everything is slided to "on"

If its iPhone 4 or later, check to see if your sound lock is on. (That little switch above the volume buttons on the side of your phone.) If its an earlier model, it's probably just getting old.