YouTube sound not working when iphone is on silent?

I've had my iPhone 4 for over a year now, and I've never had this problem. It started today, if I try to watch a YouTube video without headphones and the phone is on silent, there's no audio. But if I turn the ringer on there's audio. Obviously I've looked at the volume levels, and they're up. Like i said its only started today and it's very frustrating!

Facepalm…

When you turn it on silent everything not
Only the ringers audio should be gone! And if you didn't have that before then thats your real problem