iOS Codec Mess
In the other iOS demo you may have found out that iOS has several problems playing back encoded / compressed Audio files due to their iTunes implementation.
What you might not know: There's an AIFF audio container format using an IMA-ADPCM codec that is supported on iOS.
You can convert files to this format (on Mac OSX) via:
afconvert -f caff -d ima4 audiofile.wav