Audio Sprites (and fixes for iOS): "iPhones don't like playing too much audio at once, it gets very choppy.
iPads don't play more than one audio stream at once. There's some good info on 24 Ways, in the State of Audio - Early Findings - sadly this was published after I discovered this for myself!
iOS won't download the audio unless the user initiates the action.
There's about a 1/2 second delay before iOS is able to play the audio - this is because the audio object (in iOS, not HTML5) is being created.
'via Blog this'