[iPhone 4] Half working microphone?

Hi all

I have an iPhone 4 32GB black.
But i seem to have some problems with the microphones.
When i record a video with the iPhone, and play the video, all sound is perfect.
But when i use Voice Recorder to record sound, and play this, i am only getting a high pitch buzzing sound.
The same problem appears with skype testing service.
Recording message, playback, high pitch buzz.

This is pretty annoying.

Does anyone knows what this might be, and where to start when solving the problem?

Thanks in advance.
Cheers,
minibike12

Already went to a genius bar.
No luck .
It seems that this was an german t-mobile iPhone, and i live in the netherlands, so they refuse to help me.

But i am pretty handy with tools, so this might help.

I've read more problems with the noise cancelation indeed.
Can you tell me what part needs to be replaced?

Btw, i've noticed that most people can use skype/Voice Recorder, but can't call with their simcard.
I can't use Skype/Voice Recorder at all, only camera at this moment.

Hmm i found out that only the bottom mic isn't working.
The top mic is working with video's and speaker call.
So i think i will have to chance the mic flex?