My iPhone doesn't make the same noise when it vibrates when I take it vertically or horizontally. Besides, when i slightly shake it makes a very strange noise (cf. my video:http://www.youtube.com/watch?v=biriA93j7tU) This is my 3rd iPhone, all the others had a display problem, but this one is perfect, except this noise. Please, tell me what you think about it, and if i should take it back to Apple. (My mother has an iPhone which makes almost the same noise when shaken, but i have a friend whose iPhone doesn't make this noise...). Thanks for your replies!