AUIOClient_StartIO (-66628) error while working on the iPhone device

Question

In iOS7.1.1 (device: iPhone 5), the following error message appears:

AUIOClient_StartIO error while trying to play in the background ERROR: [0x3ce1a18c] 1202: AUIOClient_StartIO error (-66628) Error: -66628

Mine - the PitchDetector application, refers to the PitchDetectorExample project on GitHub ( https://github.com/liggitt/PitchDetectorExample )

And I tried to get audio data in the background. It works great in iOS 7 simulator, but sometimes it doesn't work on iOS device