Reminds me of some other condition, I don't recall the name. I want to say "night terrors". My oldest had serious sleep issues when he was little. So I checked some book out of the library to try to get a handle on it. Most of it was drivel, like "god, I can't believe you thought someone would need that told to them". But it did have one piece of information in it that was useful, and that was about my oldest son occasionally getting up all upset after sleeping for roughly an hour. I eventually realized he only did this when physically exhausted but not mentally exhausted. So he would fall asleep but his mind was still racing. After an hour, he would sit up basically screaming, due to very vivid mental stuff going on. The book indicated he probably wasn't really awake at such times, but was reacting while asleep. I learned to not let him get so physically exhausted and it went away. The problem never returned.

I think it would be neat if someone who has EHS kept a diary/journal and tried to determine if there was some pattern, some trigger event or whatever, for them personally (my assumption being that triggers would vary from person to person but enough such data might yield some generalizations anyway). It sounds like it may be an auditory version of the visual stuff my son experienced.