# Almost asleep...Loud sound causes flash of light
**URL:** https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875
**Category:** Factual Questions
**Created:** [April 10, 2003, 8:02pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875 "2003-04-10T20:02:29Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)
#### Post date: [April 10, 2003, 8:02pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/1 "2003-04-10T20:02:29Z")
Here’s the situation. I’m lying in bed, on my way to slumber land. As I start to fall asleep, there is a loud noise: door slamming, dog barking, anything that is relatively loud and sudden.
Suddenly, I see a flash of light. It kind of looks like television static, but behind my eyelids. It only lasts a split second, and then it’s gone.
This isn’t a one-time deal, either. It _always_ happens in the aforementioned circumstances.
Does anyone have any idea what causes this? Perhaps my brain, in its near-sleep state, decides it would be a wonderful idea to process sound as visual input?
I’m not concerned or anything, because it doesn’t seem to be an actual problem. I’m merely curious as to what causes something like this to happen, and if anyone else has experienced the same thing.
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### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [April 10, 2003, 8:12pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/2 "2003-04-10T20:12:21Z")
Does the flash of light behind your eyelids occur simultaneously with the loud noise? Supposedly, some people can sense sounds with vision in this manner. But, it seems to me this problem would be noticed all the time.
It sounds like this is a frequent occurence. You don’t live in close proximity to an airport or railroad tracks, do you? - Jinx
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### Author:  [@andymurph64](https://boards.straightdope.com/u/andymurph64)
#### Post date: [April 10, 2003, 8:17pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/3 "2003-04-10T20:17:32Z")
You are flipping into an alternate dimension.
Who won the 1999 Super Bowl?
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### Author:  [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)
#### Post date: [April 10, 2003, 8:19pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/4 "2003-04-10T20:19:55Z")
> [@](#):
>
> \*Originally posted by Jinx \*
> **Does the flash of light behind your eyelids occur simultaneously with the loud noise?**
More or less. It’s actually kind of hard to tell, because I’m always half asleep when it happens.
> [@](#):
>
> \*\*It sounds like this is a frequent occurence. You don’t live in close proximity to an airport or railroad tracks, do you? - Jinx \*\*
I wouldn’t call it frequent. It always requires specific circumstances. And no, I don’t live near anything really noisy, so that’s not an issue.
It seem that it happens every time there’s a noise that is loud enough to wake me up. And the noise has to be abrupt, not gradual. Also, it never happens if I’m actually asleep. I have to be in the process of _falling_ asleep.
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### Author:  [@Engywook](https://boards.straightdope.com/u/Engywook)
#### Post date: [April 10, 2003, 8:25pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/5 "2003-04-10T20:25:13Z")
Just a guess, but it’s pretty normal to have some mild hallucinations while falling asleep or waking up. I wouldn’t be surprised if some synesthesias were to happen to many people as well.
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### Author:  [@ForbiddenFruitsalad](https://boards.straightdope.com/u/ForbiddenFruitsalad)
#### Post date: [April 10, 2003, 8:35pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/6 "2003-04-10T20:35:56Z")
I’ve experienced the same thing. The loud speaker system connected to one of my computers will on occasion emit a rather loud “pop” 10-15 minutes after turning the computer off. I think it’s due to some kind of power saving system. If I turn the computer off right before going to bed, the sudden noise can give rise to the described “flash of light behind the eyelids”. It has happened several times.
It’s mildly irritating because it’ll wake me up, although I’ll have to admit I find it kind of fascinating too. Strange things can happen while in that half-sleep, half-awake.
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### Author:  [@Amfet](https://boards.straightdope.com/u/Amfet)
#### Post date: [April 10, 2003, 8:38pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/7 "2003-04-10T20:38:27Z")
Yep, I “see” noises too sometimes. I get it at night as you said. Usually from my TV creaking as it cools or whatever reason TV’s creak, but other sounds like thunder have done it too (and no it’s not lightening I’m seeing :rolleyes: ). I asked my SO if she gets it but she just thought I was nuts when I tried to explain it.
For me it’s typically a redish or orangish flash that I “see” before I hear the sound. I figured it’s maybe a rush of blood before you make sense of a startling noise?
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### Author:  [@Squink](https://boards.straightdope.com/u/Squink)
#### Post date: [April 10, 2003, 8:42pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/8 "2003-04-10T20:42:48Z")
You are seeing sound-triggered[phosphenes](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=129965).
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### Author:  [@Plexuss](https://boards.straightdope.com/u/Plexuss)
#### Post date: [April 10, 2003, 8:52pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/9 "2003-04-10T20:52:34Z")
I believe a good neurologist could answer your question in a flash.
(Am I a good neurologist? Well … noooo.)
However I DO know that a lot is understood about the sleep process, and a lot of bizarre anomalies do happen.
Who among us has been on the delicate verge of sleep, comfy and cozy, only to have the sudden sensation of falling - even though you’re sound in bed - ! and been violently woken up?
More rarely, who among us has been awake and aware, but totally unable to move (in that terrifying nightmare that is sleep paralysis,) possibly convinced you are dying?
In essence, many of these amonalies are a schism between your mind believing you are asleep, and your body not having been informed of this fact.
When we’re in REM sleep, our bodies want to enact our vivid dreams. Thankfully our bodies produce chemicals that keep us immobile.
Conversely, if you happen to consciously awaken while the rest of your being is paralyzed by the REM process, it can be quite terrifying.
I believe your situation is similar. While you fall asleep, your subconcsious dream apparatus is ready to go. If an outside (real) sound interferes, your subconscious might produce a
corresponding (imaginary) flash of light. However, I’ve heard of spontaneous neural discharges at the moment of falling asleep, similar to the sudden feeling of falling, expressed as a loud noise or flash of light at the moment of losing consciousness to sleep.
Hope this helps. Sorry I have no links or references. I believe that most of what I said is common knowledge, and hope that some dopers (maybe with Inet connections faster than my 12.0 Kbps!) can help you out. Your question fascinated me.
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### Author:  [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)
#### Post date: [April 10, 2003, 8:57pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/10 "2003-04-10T20:57:24Z")
I’m glad to see that this happens to other people, too. It’s nice to know that I don’t have some sort of freakishly malformed neural pasthways.
**Squink** , I don’t think these are phosphenes. From one of the site you linked to: “_Phosphene area usually ranging from 1 to 50 square degrees_”. However, the white noise that I see fills my entire field of vision.
I tend to agree with **Engywook** ’s proposal that this may be a form of synesthesias, since it _is_ linked with auditory stimulus.
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### Author:  [@ForbiddenFruitsalad](https://boards.straightdope.com/u/ForbiddenFruitsalad)
#### Post date: [April 10, 2003, 9:06pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/11 "2003-04-10T21:06:17Z")
For me it’s just a very brief, bright white flash covering the entire field of vision. No colors and no patterns. Given the effect and circumstances it does seem more likely that it’s a neurological phenomenon rather than phosphenes.
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### Author:  [@jkusters](https://boards.straightdope.com/u/jkusters)
#### Post date: [April 10, 2003, 9:45pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/12 "2003-04-10T21:45:24Z")
I have the same experience, but cannot explain it. Since I have a phobia about lightning, sometimes the “flash” can be much more upsetting than the event that caused it.
JOhn.
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### Author:  [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)
#### Post date: [April 10, 2003, 10:08pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/13 "2003-04-10T22:08:23Z")
I am so tickled to see this thread. A couple of weeks ago I had this happen to me in a dream. The building in which I live gives off some pronounced sttling noises; usually a loudish pop or two.
The thing of it was that in my dream what I heard was an incredibly loud bang accompanied by a white flash. The dream-editors that night thought it would be funny if I immediately dreamt that I was holding a bomb. And of course it killed me.
So I bolt upright in bed scared spitless. Pretty unnerving.
Thanks for letting me know I’m not a loony. (Maybe)
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### Author:  [@Squink](https://boards.straightdope.com/u/Squink)
#### Post date: [April 10, 2003, 10:27pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/14 "2003-04-10T22:27:26Z")
> [@](#):
>
> Squink, I don’t think these are phosphenes. From one of the site you linked to: “Phosphene area usually ranging from 1 to 50 square degrees”.
> However, the white noise that I see fills my entire field of vision.
Possibly not. However, unexpected sounds _can_ trigger bursts of phosphene activity. I sometimes see yellow and purple flashes, in typical phosphene patterns, across the whole visual field, under the conditions you mentioned. The noise may trigger some other phenomena with you.
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### Author:  [@Tecocat](https://boards.straightdope.com/u/Tecocat)
#### Post date: [June 6, 2014, 3:31am UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/15 "2014-06-06T03:31:25Z")
OMG yes!! I saw your post because I was trying to Google this phenomenon and find out more about it…it was tough to figure out the search terms to use…
Do you find that the flah of light or static is sometimes accompanied by a sound that.s kind of like a rubberband or a quick hum?
So what the heck is this and why does it happen to us? It’s definitely not phosphenes, based on the images that article links to. I just started taking a nerve pain killer (on top of the Tylenol with codeine and muscle relaxant that I’m on for a bout of sciatica that I’m having and this phenomenon happened to me, like, five times last night as I was falling asleep. I noticed that certain ambient noises tended to trigger it more than others.
If you ever succeeded in getting more info about this, I’d love to know what you learned!
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### Author:  [@Senegoid](https://boards.straightdope.com/u/Senegoid)
#### Post date: [June 6, 2014, 4:15am UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/16 "2014-06-06T04:15:50Z")
YES, this happens to me also quite regularly, and always has for as long as I can remember.
It doesn’t have to be a loud sound, either. Just a sudden or sharp sound, whether it’s loud or not.
You know how incandescent light bulbs, when turned off, will make occasional “tink” sounds as they cool? Not loud at all, but a fairly sharp and sudden sound. I always saw those sounds as a flash of light. This happened while I was sort of partly asleep, with my eyes closed.
So for a long time, I thought that the cooling bulb actually did emit a flash of light simultaneously with that sound. I wondered what physical principle could account for that. Was it some kind of strange quantum effect? When it cools enough to go “tink” does it emit a puff of photons?
I asked a friend about it about 35 years ago – a guy who I felt would likely be knowledgeable about such matters. He said he couldn’t imagine a reason why that would happen.
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### Author:  [@sidecar\_jon](https://boards.straightdope.com/u/sidecar_jon)
#### Post date: [June 6, 2014, 2:45pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/17 "2014-06-06T14:45:49Z")
There is the dramatically named “Exploding head syndrome”…
> **[Exploding head syndrome](https://en.wikipedia.org/wiki/Exploding_head_syndrome)**
>
> Exploding head syndrome (EHS) is an abnormal sensory perception during sleep in which a person experiences auditory hallucinations that are loud and of short duration when falling asleep or waking up. The noise may be frightening, typically occurs only occasionally, and is not a serious health concern. People may also experience a flash of light. Pain is typically absent.
> The cause is unknown. Potential organic explanations that have been investigated but ruled out include ear problems, temporal...
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### Author:  [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)
#### Post date: [June 6, 2014, 3:40pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/18 "2014-06-06T15:40:28Z")
I wonder if zombie threads see a bright flash of light when they’re yanked back up to the first page of results.
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### Author:  [@Hypno-Toad](https://boards.straightdope.com/u/Hypno-Toad)
#### Post date: [June 6, 2014, 5:45pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/19 "2014-06-06T17:45:07Z")
This happens to me sometimes. If a certain lamp is cooling and goes “tink” at just the right moment, my entire field of vision is filled with a perfect checkerboard pattern of light and dark squares for a brief instant. Rarely, the checkerboard will be at a 45 degree angle creating a dimond pattern.
Zombie or not.
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### Author:  [@Senegoid](https://boards.straightdope.com/u/Senegoid)
#### Post date: [June 6, 2014, 8:27pm UTC](https://boards.straightdope.com/t/almost-asleep-loud-sound-causes-flash-of-light/167875/20 "2014-06-06T20:27:00Z")
> [@Hypno-Toad](#):
>
> This happens to me sometimes. If a certain lamp is cooling and goes “tink” at just the right moment, my entire field of vision is filled with a perfect checkerboard pattern of light and dark squares for a brief instant. Rarely, the checkerboard will be at a 45 degree angle creating a dimond pattern.
That’s fascinatingly artistic! When I hear a light go “tink” I just see a brief flash of light with no pattern to it.
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