AVAudioRecorder allows the recording of external audio. However I wish to record the audio made by my application (through numerous AVAudioPlayers), is this possible on the iPhone?
If you want to record the sounds your iOS app makes, you have to use a much lower lever API, such as Audio Unit RemoteIO, or Audio Queues with raw PCM audio samples.
来源：https://stackoverflow.com/questions/5670326/is-there-a-way-to-record-device-audio-on-the-iphone