iPhone 4 recording video - sound quality

I have recently been taking more videos than photos with my iPhone 4 but noticed the sound is barely audible. Am I doing something wrong or is there a setting I need to set?

I have no issues with talking on speaker sphone, play music, or watching shows through the speaker but when it comes to quality from recording a video I can barely hear it when playing it back.

Is this a known issue or has it happened to anyone else? Is it possible that there is something wrong with my iPhone 4? I did a search on the forum but didn't come up with anything.

Any idea?

The thought did cross my mind but I confirmed I wasn't by doing other tests and I still get the same results.

I also found a video when I first purchased the iPhone 4 and it sounds great and there are no issues. Is the mic for recording the same as when I record voice memos? I have no issues with sound quality when recording and playing back voice memos.

I actually meant to say I did a quick video when I first bought the iPhone 4. It didn't come with one.

There were no quality sound issues with the voice memos but just with the videos I was taking.

I took my wifes iphone 4 and did a comparison as a test and confirmed her sound quality was a lot better than mine. I did another test by covering each mic so I can narrow it down. I found the sound quality didn't change on my wifes when I had the bottom covered but it did change when the mic on the top was covered. I went back to my phone and blew in the top mic and banged gently to see if there was anything maybe blocking it. I took another video quality and found that its now working! I guess something got in it or was blocking it and I didn't notice it. I'm Happy again!