With AVAudioRecorder, we can create different audio files in different format. So how could we determine which format we should use?

i found a blog post which could give you the answer. The author Tonny has tried different kinds of audio formats and you could find the results at Best Audio Format for iPhone Audio Programming.

Thanks for his great work. The best audio format should be kAudioFormatMPEG4AAC but unfortunately, this only works in iPhone simulator. So i decide to use kAudioFormatAppleIMA4 format in my iPhone app.
 

Reference: Best Audio Format for iPhone Audio Programming