We used to play games with each other(no SLF & over jungle), when one of us fell asleep the other would shout "turning", which meant you had already missed your marker, the look of terror was a sight to behold.
When your having a microsleep it's always the unexpected sounds that wake you, in this case the CC calling. Any sound that is expected can be quite loud and you miss it.
Your limbic brain still operates when sleeping, the best solution would be a sound that is different each time.