In the second episode of Fringe’s third season, Walter, Peter and Fauxlivia are called to investigate a crime scene that, on the surface, appears to be a robbery, save for a few minor details: the burglars are still in the house, they’re frozen in a kind of trance, and whatever they were trying to steal is gone.

The team discovers the stolen object is a box that emits a sound, puts anyone within earshot into a trace, and then, eventually, kills them. The man who stole it was deaf, which explains why he wasn’t affected. By shooting a gun near Peter’s ears, Walter temporarily deafens him, which allows him to find the box and disable it.

There aren’t any real-world killer music boxes that have the ability to put us in a catatonic state before killing us (at least, as far as we know), but sound does have profound effects on our brains and our bodies.

The Brain

Though it’s a long way from a sonic killing machine, one of the most interesting (and somewhat mysterious) examples of the effect of sound on the brain is music.

In his book This Is Your Brain on Music, Daniel J. Levitin explains our interpretation of sound in simple terms, saying, “Sound is transmitted through the air by molecules vibrating at certain frequencies. These molecules bombard the eardrum, causing it to wiggle in and out depending on how hard they hit it (related to the volume or amplitude of the sound) and on how fast they’re vibrating (related to what we call pitch).”

He goes on to explain how our brains decipher auditory information to determine where sounds come from and what they mean, and how and why car horns might make us alert while long, slow notes can be calming.

We’ve broken down our brains and music further, noting that the structure of songs is a big part of what affects our brains so profoundly that it creates a physical response. The secret? Stress.

Song structure and the meaning we put behind certain songs can elicit powerful responses as those molecules bombard our eardrums, giving us goosebumps, sweaty palms and even a dopamine rush.

Levitin expands upon the idea of structure, saying:

“Perhaps the ultimate illusion in music is the illusion of structure and form. There is nothing in a sequence of notes themselves that creates the rich emotional associations we have with music, nothing about a scale a chord, or a chord sequence that intrinsically causes us to expect a resolution. Our ability to make sense of music depends on experience, and on neural structures that can learn and modify themselves within each new song we hear, and with each new listening to an old song.”

The Body

Though sound has the power to affect our brains so deeply that it can elicit a physical response, the effect that sound can have on our bodies is another matter entirely. Here we’re talking not about a neurological response that becomes physical, but the degree to which frequency and volume can affect us on a physiological level.

In an excerpt from his book The Universal Sense: How Hearing Shapes The Mind that appeared on Popular Science, Seth S. Horowitz discusses the physiological effects that sound can have on our bodies. More specifically, he tackles infrasound, or the question of whether or not acoustic weapons are theoretically sound.

Infrasound is low-frequency sound that’s below 20Hz, meaning it falls outside of the range of human hearing. Horowitz points out that this sound — like any other kind of sound is going to have some powerful effects once it into high decibel ranges (140 dB and beyond). Though he debunks the existence of some seriously sinister sound studies from a French researcher named Vladimir Gavreau, he explains that infrasound has characteristics that don’t totally rule it out as a weapon.

“The low frequency of infrasonic sound and its corresponding long wavelength makes it much more capable of bending around or penetrating your body, creating an oscillating pressure system,” says Horowitz. “Depending on the frequency, different parts of your body will resonate, which can have very unusual non-auditory effects.”

He uses the example of your eyeballs, which resonate 19Hz. If you were to sit in front of a subwoofer playing a tone at 19Hz and crank it up to 110 dB, you might start seeing some truly bizarre stuff — colored lights and maybe shadowy figures. Even at relatively normal volumes, your eyeballs will begin to twitch at that frequency.

It’s not just our eyes, though. Our clumsy flesh containers have all kinds of resonant frequencies. Our skulls (minus the flesh and brains), for example, have acoustic resonances at 9 and 12kHz, 14 and 17kHz, and 32 and 38kHz. For the most part, those frequencies don’t require highly specialized equipment to emit. So could they be used as a weapon to make someone’s head explode?

Theoretically, maybe, but not at all practically. For a skull that’s brains and all, things change.

“In fact, when a living human head was substituted for a dry skull in the same study,” says Horowitz, “the 12kHz resonance peak was 70 dB lower, with the strongest resonance now at about 200Hz, and even that was 30 dB lower than the highest resonance of the dry skull. You would probably have to use something on the order of a 240 dB source to get the head to resonate destructively, and at that point it would be much faster to just hit the person over the head with the emitter and be done with it.”

Just to illustrate, the highly specialized acoustic test chamber at NASA’s Goddard Space Flight Center is capable of producing sounds up to 150 dB for severe sound tests like the one administered to the James Webb Space Telescope. So 240 dB? That’s crazy high. Not exactly something we might be able to fit into a killer sound box.

Even so, it’s abundantly clear that sound can have incredible effects on our bodies, even if said sounds sound silent.