IPhone 3G S plagued by sound issues (confirmed).
OK if you lock your home screen and put your ear to the speaker you should be able to hear a high frequency sound. I tried it on my 3G S and the sound was defiantly there!
Article: http://www.boygeniusreport.com/2009/06/20/iphone-3g-s-plagued-by-sound-issues/
Article: http://www.boygeniusreport.com/2009/06/20/iphone-3g-s-plagued-by-sound-issues/
MacBook (unibody), Mac OS X (10.5.7)