It'll be awkward when they discover a new syndrome where your head explodes and the name's already taken.

Sometimes sound, sometimes an impact. Either way it’s pretty disruptive. I thought this was very common.

Hmmm, never really thought about this, but I have this happen every now and then. From what I remember it sounds like a sudden snap or click, but I don't have concrete memory of the sound. Also with a bright flash of light. Just a sudden sensory spike. I don't have good memories of it, because it usually happens just when I really start falling asleep and at that point memory usually isn't working well. It's also often accompanied with my muscles suddenly activating, basically jolting me awake. Heart rate spikes as well, but I cannot really remember any instance where it was more than a small nuisance. I always assumed that it was just a bit of a race condition in the transition to the deeper sleep state

Maybe time to write an issue to the development team for the brain OS :p

Wow! Now I have a cool name to this phenomenon. Doesn't happen every night and there are also times I can ignore it because it's typically not scary, just disruptive. I also see the flashes of light and that can be scary sometimes. I'll think somebody tried to come in while I'm sleeping or that a nuclear bomb just went off. Or that a cosmic ray hit my eyeball.

Now, is there a phenomenon about seeing random faces in my head while falling asleep as well?

When I was deployed in Afghanistan, everyone I knew had the same reoccurring dream- some other dream is happening, and then out of nowhere, you hear a gunshot/explosion, and wake in a cold sweat, absolutely certain that you just got shot or blown up. And the certainty persists for about five seconds after you wake, as you shakily pat yourself down for blood. Good times.

This made me double check, but it's still just that I have loud children.

I don’t know if this qualifies, but I go on call for my job and get woken up sometimes. I use a really annoying alert tone to make sure I wake up. Unfortunately, some times when I’m not on call I hallucinate hearing that tone as I’m dozing off or in a dead sleep and it makes me shoot straight up in bed.

I used to have that when I was a teenager. About one out every ten times I was falling asleep just at the moment I drifted off I'd feel this crazy big pop that went from deep behind my right eye to the top right part of my skull. Sometimes it was more like a noise, sometimes it was more like a physical impact, like somebody bounced a golf ball off of my skull. It was really annoying. It started to happen less and less as I got older though. It pretty much went away completely by the time I was in my late 20s.

I get this from time to time when falling asleep. It's really annoying when it happens. Like I'll be dozing off and then there will be this loud-ass noise.

Me.

It's an explosion in my head.

Like this : imagine a sound. For example, a cat meow. Meow meow. You doing that? Are you "hearing" that meow in your "mental sound space"?

Now imagine the sound is 500x louder. And it isn't a meow, its an explosion.

It sounds like the blast of compressed air when you disconnect a compressor fitting.

That's what it's like.

It happens in half-sleep.

I've had big blasts that make me go "woah" a couple times a month since forever. I had a really big blast that made me go "holy shit!" just a couple days ago.

Wait, is this my "nightmare sound"? When I have nightmares (fairly rarely, but I've gone through times when they were more common) there's a sound that goes with them, and builds in intensity as the fear comes to a crescendo. It's like a high-pitched whine that starts as a hum (like tinnitus) and slowly grows to ear-splitting intensity, except it's more like head-splitting because it feels like the origin is in the center of my head. And I say "feels" intentionally because it's not just a sound, it feels like my consciousness is vibrating apart.

Often the actual content of my nightmares is mostly abstract (like worrying about why the room is dark, or feeling followed but not knowing by what) and the terror is completely disproportionate to the events, but directly proportional to the intensity of the sound.

Uh, for me it's firmly inside the dream though, I wouldn't classify it as a hallucination. When I was taking antidepressants I used to have hallucinations wake me up—like waking up because I heard my mom talking, when she was in a different state—but that felt different. That was like hearing someone in the room with you and having it pull you out of whatever dream you were having. The "nightmare sound" is inside the nightmare, it isn't what wakes me up.

For me, it sounds exactly like a wooden screen door slamming shot.

Whoa this is so interesting!

I've been having them on and off for as long as I can remember. I seem to notice I suffer them more often when sleep deprived and also when playing long hours of videogames (or both).

To me, it sounds like someone screaming into my ear.

I have that. I call it "shitty neighbour syndrome".

For why this is happening to me, I've narrowed this down to the following: snoring (I start snoring as soon as my eyes close), dreams (I have "imaginative" dreams, a lot of nightmares) and the last reason being lack of sleep to which I think I've actually heard the explosion but it was a dream.

I get this sometimes. Kinda weird, but ultimately not a huge deal.

This happened to me for about a week. I've never had it since.

I get it too but only if I'm trying to fall asleep on my back. 3 weeks ago I got a really strong one, I could still feel the shock in my brain for a minute after.

Hypnic jerk with synesthesia?