I just discovered something and I wanted to double check with someone my observation.
I have just made my own CocosDension but quite similar to your one in interruption area
And I see interruption behaves strange - I don't know whether this is IOS behavior or something else
on method: audioSessionResumed add as first line:
and check value.
on iPhone 5S IOS 7.1 & iPhone 4s IOS 5.1
I see value a003
on iPhone 3gs iOS 5.1
value is 0
openAL play wave sound in loop
use another phone to call to test device and while test device start ringing, hang the second phone, and check the error value.