if you are talking about the red banner on the top of the screen which says that the AD 480 is recording, do not worry about this. When an app has access to the iDevices recording facility, which could be the internal mic or an input of an audio interface, this red banner is shown by iOS in case the app has primary access to the audio system. If the app is in background and no audio is processed it does not use up more resources than any other app in the background. Generally it is recommended to terminate (not just send to background) any app not in use.
So the behaviour is standard for audio recording enabled apps. Nothing to worry.