Why is the sound not recording?

I have had an iPhone 4 for quite a while now, and I've never had this problem before. When I record videos, the audio doesn't get recorded, and when I play back the video, all I hear is a loud hissing sound. I know that this isn't a problem with iOS 7, because it was perfectly fine when I first updating the OS. I'm really confused.

According to this thread, it has something to do with the way the iPhone 4 was designed:

https://discussions.apple.com/...ad/2490559

You can try to listen to the video you recorded with headphones, or try copying the video to your computer to see if the hissing sound is still there. It's also possible that the microphone is clogged with dirt, which would prevent it from being able to pick up audio. The hissing could be a result of the automatic audio gain trying to compensate for the lack of audio the microphone is picking up.

Its probably how you have an iphone 4 and running ios7 cuz stupid things happen when you have a old model phone and a new software running on it if you get wht i'm saying