There is a lengthy thread about it at the Apple Discussion forum and quite a few upset 3GS users. The simple truth is that the progeny of the iPod and a telephone is plagued by none other than poorly implemented system sounds. What has been characterised as ‘whiny’ and ‘squeaky’ is an issue with feedback between the mic and speakers. For the moment, manual fixes are possible by tweaking the volume of both the mic and speakers, but nothing so Apple-esque that it ‘just works’. Apparently, the Apple Store ‘Genius Bar’ has been soused in Apple’s extra fizzy drink as they are mum about Apple’s mistaken programming, citing rather, faulty hardware, thus delivering the problem into the hardware manufacturers.