Just a quick note, if you get undocumented errors from CoreAudio while running your app in the simulator, make sure you don't have any QuickTime components laying around.
I kept on getting 'perm' , 'fmt?' and '????' errors when using AudioConverterNew, AudioFileReadBuffer and AudioFileWriteBuffer, and had to remove all items from /Library/Quicktime/Components [and reboot].
Do back them up though...
Enjoy CoreAudio in the simulator :)