SMS alert when audio recording application is running iOS

I have an audio recording application. If an SMS alert comes, I don't hear the alert's sound. The recording continues to happen. I can also go ahead and reply without affecting my recording at开发者_如何学运维 all. That's a great thing. But, how does this happen? Isn't the SMS considered as an interruption to the audio session?

Pete Goodliffe has written an article that might help you at http://goodliffe.blogspot.com/2010/11/make-some-noise-audio-on-ios.html. Of course, Apple documentation on Audio interruptions describes the interruptions management.