Could the Sound Illusion Discs of Five Nights at Freddy’s Actually Work? (2024)

The technology in the Five Nights at Freddy’s franchise has always been way ahead of its time. (Bipedal robots in the 80’s anyone?) But one piece of tech seemed to be a step too far: the Sound Illusion Discs.

This contentious piece of tech– introduced in the original Five Nights at Freddy’s novel series, first appearing in The Twisted Ones and again later in The Fourth Closet– uses sound to make people see spooky monsters. The novels describe the Sound Illusion Discs working as such: they emit a rapidly-changing series of high-pitched frequencies that are outside the range of human hearing, but can still be perceived by the subconscious. These sounds confuse the brain into making you see things that aren’t actually real. In the books, the main thing they’re used for is making the titular twisted animatronics look like scary monsters or regular friendly animatronics, depending on the situation.

However, in the end (spoilers), when the discs are turned off, the twisted animatronics are revealed to be nothing but bare endoskeletons being disguised by these sounds. So basically, these discs use sound that you can’t actually hear (but sort of can) to make a specific object look like a different object.

These discs also have an effect on cameras; anything being cloaked by one will appear blurry in photographs and videos, and aside from the whole hallucinating thing, prolonged exposure to these sounds can make you feel nauseous, but are otherwise relatively harmless.

In general, FNAF fans hated the Sound Illusion Discs. Boy oh boy, did they hate them. But are the Sound Illusion Discs really that much more far-fetched than spring lock suits or rogue AI that can take over your brain? Or are they more grounded in real-world science than any of us gave them credit for?

Let’s start from the top, with high-pitched noises that you can’t hear, but your brain can still perceive. The pitch of a sound is related to its frequency, or how fast that sound wave is waving. A higher frequency, measured in Hz, correlates to a higher pitch. Humans can typically hear sounds ranging from 20 Hz on the low end to upwards of 20 kHz on the high end. This differs from person to person and worsens as you age, but in general, if a sound has a frequency higher than 20 Hz, we can’t hear it.

However, studies have shown that our brains do experience a change in electrical activity when exposed to sounds of 22 kHz and above. What does that mean? It means that FNAF was actually spot on! There are high-frequency sounds that our brain can detect and react to, without “hearing” it! (Well, they were spot on about this one thing. They were wrong about pretty much everything else. You’ll see.)

This phenomenon is called the Hypersonic Effect, and apparently, it’s more pronounced when you layer inaudible high-frequency sounds on top of regular audible frequencies. As an example, according to a study published in the National Library of Medicine called “Inaudible high-frequency sounds affect brain activity: hypersonic effect,” people tend to find music with high, inaudible frequencies layered on top more pleasant to listen to than the same song without them, even if they sounded functionally identical.

Effects of exposure to high-frequency sounds can vary greatly, ranging from mild annoyance to ear pain and temporary hearing loss to nothing at all. However, while researching possible side effects, I didn’t find a single reported case of someone experiencing any sort of visual hallucination or change in their perception at all when exposed to any of these sounds. So as far as finding the real-world science behind Sound Illusion Discs, we’ve run into a bit of a dead-end with the high-frequency sounds.

And yet, if we hop to the other end of the spectrum and consider sounds that are too low for us to hear, we find something very sinister indeed. There is one frequency– one specific, impossibly low note, of 18.98 Hz– that is just barely below the range of human hearing. This sound, if you can even call it that, has been documented to induce feelings of dread and panic in any who listen to it. This sound can cause people to see shadows moving around at the edge of their vision, only to look and realize that there’s nothing there. And the name of this unholy tone? “The Ghost Frequency.”

Although it’s a real, documented phenomenon, “The Ghost Frequency” is not nearly as spooky as it sounds. The exact reason why people experience these sensations when exposed to this specific frequency is up for debate, but the most commonly accepted explanation is that it closely matches the resonant frequency of the human body. So this sound will subtly vibrate your body or cause you to shake every so slightly, which might give you a chill. Or it might make your chest feel ever so slightly tighter, making it a little harder to get a full breath, which is where the feelings of dread and panic come from. It can also slightly vibrate your eyes within their sockets– not to any dangerous level, but enough to make shadows seemingly dance at the edges of your vision.

Interestingly, this sound comes up more often than you might think. For example, in historically “haunted” places (old hotels, decrepit mansions, stuff like that), it’s often discovered that an old air conditioning unit or some pipes grinding together under the foundation were emitting this frequency. And apparently, certain animals like tigers have been known to emit this low-pitched frequency in their growls to intimidate their prey while hunting, causing them to freeze up so they’re easier to catch. (In case tigers weren’t terrifying enough, they just had to throw paralyzing roars in there!)

Now, back to FNAF’s Sound Illusion Discs. At a glance, this real-world science of the Ghost Frequency seems super promising: a sound that we cannot ordinarily hear, albeit a low sound instead of a high one, that can fill you with dread, and even cause visual hallucinations! Great! Sound Illusion Discs are solved!

Not so fast: the effects of this “Ghost Frequency” vary greatly from person to person, and most people don’t even react at all. It can cause visual alterations, let’s say, but they are completely random; everybody sees something different, and nothing as crystal clear as a full robot bear!

It’s also important to note that these visions occur due to the vibration of your eyes, so it wouldn’t make sense for the vision to be locked to a specific object like the endoskeletons in the books; rather, it would follow you wherever you look.

So it looks like the whole “sound” angle has turned up a whole lot of nothing. Sure, there are sounds outside the range of human hearing that can have subtle effects on the brain and body, but nothing even remotely close to the sorts of controlled visual hallucinations that we see the Sound Illusion Discs produce.

But perhaps we’re approaching this from the wrong angle. We know sound can’t cause these sorts of illusions… but then again, can anything? Is an object appearing as something completely different even possible? In one last-ditch effort to make the Sound Illusion Discs make even a lick of sense, I went back to the research grind, and came across a little thing called Hypnopompic Hallucinations– or, in layman’s terms, the sleep paralysis demon.

Sleep paralysis is something that can occur when you are abruptly woken from REM sleep. While in this deep sleep state, your body paralyzes itself to give your muscles some rest. But sometimes when you quickly wake up in this state, it takes a couple minutes for your body to catch on to the fact that you’re not still sleeping, and some weird things can happen before it does. Not only can people not move most of their body, but many also report seeing distorted figures– or “demons,” as they’re often described– in the low light of their bedroom. These can be wholly new apparitions, but more often something already in the room– like say a lamp, an alarm clock, that bare endoskeleton you have lying in the corner– will become twisted into a nightmarish humanoid monster in the mind of the sleeper.

But why demons? Your brain misinterpreting what you see shrouded in dim light in this strange half-sleep state makes sense, but why do so many people report seeing demons and monsters specifically? It’s generally believed that people see these scary demons for the same reason people have nightmares. Anxiety, stress– these things that plague your mind while you’re awake stay with you when you’re asleep and can manifest as these scary apparitions.

Scientists have also theorized that people are inclined to see humanoid demons specifically, because of something we all possess called Facial Pareidolia. Humans are really good at spotting faces and reading them for emotions. Sometimes we’re too good at this, to the point where we see faces in places that aren’t there. So in your half-dream state, that clock might start to look a little like a twisted, shadowy face. (Some folks theorize that these apparitions don’t look like demons, but rather the classic look that we associate with demons came from these Hypnopompic Hallucinations.)

Now let’s combine the phenomenon of the “sleep paralysis demon” with what we learned before. We know that the Ghost Frequency can induce feelings of anxiety and dread, and anxiety can lead to sleep paralysis demons manifesting. Could there be a connection– with the sounds leading to stress, the stress leading to the demons? Of course, this would only work when someone is in a very specific, difficult-to-replicate state of being both awake and asleep, and in the books it’s used on people who are very much awake. So that doesn’t make much sense.

But what about Five Nights at Freddy’s 4 game, which features a kid in his room, being attacked by the Nightmare Animatronics? Now, some fans have theorized that the Nightmare Animatronics in this game are using these Sound Illusion Discs to alter their appearance, very much analogous to the Twisted Animatronics from the books. (I know a recent short story said that the nightmares used hallucinogenic gas, because we bullied them too much about the sound discs.) But think about it: A kid in his room in the middle of the night is abruptly roused from a deep sleep by a sound in the hallway, the footsteps of an animatronic emitting a low-frequency sound that he can’t quite perceive. This sound is the Ghost Frequency, which triggers his anxiety. This feeling causes his half-asleep brain to see these ordinary animatronics as twisted, nightmarish versions of themselves.

In summary, with some sci-fi pushing of boundaries, here is exactly how the Sound Illusion Discs could work:

• The Sound Illusion Discs emit a series of sounds just outside the range of human hearing, both on the high end and the low end (not just high-pitched sounds, as the books suggest).
• These inaudible sounds– layered on top of each other, since that increases the hypersonic effect– can influence the listeners’ brains and alter their moods.
• This mood change can then change the quality of the listeners’ hypnopompic hallucinations: high-pitched inaudible sounds– the ones which make music seem more pleasant– could make them see happier, friendly animatronics; meanwhile, the low-pitched Ghost Frequency– which fills listeners with dread– would make the animatronics appear demonic and evil.

The only real logical leap that we need to make is assuming that hypnopompic hallucinations could occur in someone who’s fully awake and not in a state of sleep paralysis, which admittedly is a pretty big jump. But this is also a story about ghost kids possessing high-tech robots made by a crazy person, so, you know, I’ll let you decide where to draw the line.

So, yes, Sound Illusion Discs do have a backing in real-world science, but it’s some very obscure science that I’m pretty sure that FNAF creator Scott Cawthon ducked into. Ultimately, there is no real science-backed answer that can explain ALL of the Sound Illusion Discs’ weird abilities. (Heck, I haven’t even mentioned the camera thing, because that makes absolutely ZERO sense.)

But, then again, not everything in sci-fi makes sense. A lightsaber blade stopping after a certain point? Instant teleporters from Star Trek? Animatronics from the 80’s that can walk around on their own? None of these really make sense, but there’s enough real-world science sprinkled in there that our imagination can fill in the gaps. And from that perspective, maybe the Sound Illusion Discs are in the same boat. Maybe they’re just as cool as a lightsab- I’m sorry, I can’t finish that sentence. Nothing, after all, is as cool as a lightsaber!

To learn more, watch this video on my YouTube channel, TheChiptide. On my channel, I apply science and math to many other video games, such as Pokemon, Metroid, and Mario Bros. Thanks!