I can't hear videos on my iphone 4

Recently I was making a video then when i was finished filming I wanted to check it out. So before I unlocked my phone, I viewed it. I could see the tape, its just I can't hear anything! I checked the left side to be sure of removing the vibrate/silence button but its just not working! But when I look at my old camera roll, I could listen to the other videos! I can hear music, youtube, any other apps at ease, but I can't seem to hear the videos I just made or probably wouldnt be able to hear the ones in the future.

Turn up your ringer volume