Ghost stories, do they ever give you the creeps? Let’s take a journey back to the early 1980s. Vic Tandy was a guy working at Warwick Labs in the UK, designing medical equipment. The place had a reputation for being haunted, but Vic thought the spooky vibes stemmed from the hums and beeps of life support systems. However, one late night in the lab, strange stuff started happening.

Vic felt his neck hairs stand up, broke into a cold sweat, and got this intense feeling of dread like someone was watching him. His heart was racing, and then, out of the corner of his eye, he saw a grey figure float across the room. When he turned to look, it was gone. Freaked out, he bolted from the lab and dashed home. Once he calmed down, Vic promised himself he’d find a scientific reason for the spooky spectacle.

But did he figure it out? You bet, but it wasn’t a ghost hunt. The next day, he noticed something really odd. Vic was a fencer, and his foil was clamped in a vice and vibrating like crazy. What ghost does that? Turns out, a fan had been recently installed in the lab, and it was causing some sound waves to ping around the walls. These waves hit just the right spot where Vic stood and where his foil was clamped.

What’s wild is that these sound waves were at around 19 hertz. To you and me, that’s just below what we can hear—around 20 hertz and up. So, we’re talking infrasound here, sounds too low for human ears but not without effects on us. Ever noticed how certain sounds can resonate with physical objects? It’s why a wine glass might hum when you run your finger around its rim. Same deal here.

In the lab, it was like a ghostly illusion because the human eye resonates at about 19 hertz. That strange apparition Vic saw? Just his eyeball vibrating! The noise was also messing with folks’ emotions, causing fear and anxiety. When they turned off the fan, it was like lifting a giant weight off their shoulders.

Turns out, these low frequencies don’t just mess with humans. Tigers use a similar trick. Before attacking, their roar has those low frequencies—specifically around 18 hertz—to disorient prey enough for them to make the kill. Horror movies have caught on too, using sounds just at or above this fear frequency to up the scare factor.

So, what happens if we go lower? Say, at the infamous brown note range, between five and nine hertz. This theoretical frequency is said to make people lose control of their bowels. Crazy, right? Yet, there’s no solid proof. The MythBusters guys tested it with huge speakers and didn’t quite get the results, though Adam Savage didn’t feel too hot afterward.

Here’s where it gets gnarly. Sound, particularly these low frequencies, can harm in ways that are more than unsettling. The space program ran tests with the brown note, connecting vibrations directly to subjects’ bodies. The sound levels were off the charts—160 decibels. These tests resulted in nausea, hallucinations, breathing difficulties, and there were no reports of anyone literally having an accident, but you get the picture.

You don’t need space-age gadgets to feel these vibes. People living near wind turbines often report all kinds of ill effects, from headaches to extreme stress. Although studies, mainly by turbine companies (surprise, surprise), deny any direct link, the stress caused by constant noise has real, measurable effects.

So, could sound be used as a weapon? Absolutely. The most dangerous frequencies hover around seven hertz, aligned with the brain’s rhythms and the resonant frequencies of many organs. At high volumes, these sounds mess with the central nervous system, inducing panic, convulsions, vomiting, and with prolonged exposure, even organ failure.

One notable figure, Vladimir Gavro, got into sound research back in the late ’50s and wound up making infrasound weapons. During experiments, one researcher tragically died, his organs turned to jelly from the vibrations. Even folks at nearby labs were sick for hours—true horror show stuff.

While infrasound terrifies us, there’s also ultrasound—those high frequencies beyond our hearing. Ultrasound can heat human cells and create tissue bubbles through a process called cavitation, leading to damage similar to “the bends” suffered by divers. The US Navy even uses ultrasonic weapons to fend off pirates.

But have these sonic tactics been turned against us? Havana Syndrome, a mysterious illness hitting American diplomats worldwide, suggests they have. Symptoms mimic those from sonic or microwave attacks—migraines, dizziness, and memory problems, with some needing extensive medical care. Though no official culprit has been named, whispers point toward Russia, even as investigations continue.

Havana Syndrome remains a mystery. The CIA and other bodies are on the case, determined to uncover the cause. Yet, it’s clear that the symphony of sound can play some seriously haunting and harmful notes. So next time you hear something that scares you, it might just be a sound you can’t even hear.