How to move sound from left to right of earphones in iPhone?
On IPhone 4 iOS 5.0 if you go to general, then accesablility and scroll down, there is an option to do what you need
I think you want the pan property of the AVAudioPlayer. Check the AVAudioPlayer documentation
From the pan property:
By setting this property you can position a sound in the stereo field. A value of –1.0 is full left, 0.0 is center, and 1.0 is full right.
Check out the sample app on Apple website: oalTouch