This is really annoying, had mine for 6 months now and it's a horrible high pitched buzzing noise every time I call since I had it, makes me want to end the call every time. It's a great phone for everything other than why it exists in the first place, telephone calls.
Now you may be wondering why I still have it after 6 months in that state. I live in Belgium and bought it from my ISP and they have third party to deliver the Iphones and I called them and they said they would have to send it away for minimum one month!! This I find outrageous. So will have to buy the 5 and then I can send it for repairs. Not good Apple.
Don't suppose there is a simple fix for this?
This is the noise - just found a clip:
http://www.youtube.com/watch?v=Bf0r1QRW8q4