Ok, i'm going to sound like a nutter, but when i put my N95 to my left ear whilst on a phone call i can hear a very high pitched noise. When I put it to my right ear there is no such noise. This also happens when I use my friends N95.
Clearly its something to do with the hearing pitch range in each of my ears, but surely there shouldn't be a high pitched noise at all in either ear? (My mate confirmed he too experiences this)