Robj and Gracely - thank you for your responses.Robj - I don't think what your describe is anything similar to what happened to me, so no, it might not be related to what you are thinking. What happened to me is to a T what is described in the wiki article and it is related to hypnic jerks - common amongst us. As Gracely says - related to a hyperexcited central nervous system, so definitely related in that way. I posted because it seems it might not be uncommon here anyway. And even if some haven't posted in the past, it will be here for any future members who search. This was not a true hallucination. It was more of a loud "bang, wzzz" noise, like an electric spark and LOUD and fast/brief like a gunshot. A bit frightening, but not spooky like halloween spooky, more like startling. Sometimes it is accompanied by sleep paralysis which I've seen rather common here. I was tired enough to fall right back to sleep so I'm not sure if I felt paralysis or not. I didn't try to move. And have had enough odd things now to not freak out about it like I might have a year ago. This is maybe getting closer to acceptance of "whatever will be will be." Staying awake to worry about it or figure it out won't help me now, I made a mental note to worry about it later. So I did bravely or stupidly google the next day. My intuition told me I'd find something related to my central nervous system, and I did. Nothing too scary, though it certainly could have been. I was secretly afraid it was a sign of a brain tumor and nothing like that came up. Thank God!So, here it is for the archives or anyone who might have interest.