I searched the forum and could not find anything about this. I was excited that I could turn up the receiver speaker a lot louder than my old 2g iPhone, but when I turn it up loud I get a lot of what sounds like vibration noise when the other party speaks. It's almost like that metal mesh inside the speaker hole is not secured and is vibrating against something. It would not be a big deal except for the fact that one of the main reasons I upgraded was because I was never happy with the speaker volume of the 2g and I was happy that those days would be over. I can turn the volume down and the problem goes away, but then I'm back to the problem (only problem) I had with my 2g. And.. that vibration noise is like nails-on-a-chalkboard to me, which kinda sucks. I have two iPhone 4's, one for me and one for my wife. I tested out my wife's phone and it does not do this at all. I guess I'll try a reset to see if that does anything, but I might have to go talk to a genius dude to see if I need to get a replacement. btw, I LOVE the iPhone 4... going from the 2g to 4 I get the same sense of awe that I got as a first day buyer of the 2g.