Have you ever had to put a horror movie on mute? Maybe your anticipation of jump scares made you cover your ears or pull a blanket over your head. Or maybe the slow build of the soundtrack alone was enough to make your stomach churn and send chills down the back of your spine. 

The science behind musical stress measurement

If you’ve ever been shaken by a horror movie’s musical score, you are not alone. Slow musical builds and sudden percussive notes in film scores can cause a real physical response in listeners.  

In a 2022 study by Germany’s University of Giessen, researchers discovered that scenes from horror movies elicit a higher skin conductance — how well electricity can move through the skin — in viewers when they are layered with intense music than when they are viewed without music. 

This means that during these scenes, the viewers’ skin was better able to conduct electricity. According to a 2019 study by Turkey’s Bogazici University, the human body begins to sweat, increasing the electrical conductivity of the skin in response to stressors — like those experienced in an office environment or under a time constraint. 

By attaching two electrodes to the skin and measuring the strength of a small electrical current running between them, researchers are able to take an indirect measurement of the stress experienced by horror movie audiences.

Cringing from creepy sounds

Sound effects can have the same effect as music on horror audiences. From the wildly unique and abstract noises in Stranger Things to the familiar terrors of Quint scraping his fingernails across a chalkboard in Jaws, every horror movie fan knows that all kinds of discomfort can be stirred with the right noise. 

A 2011 study presented by the University of Vienna and the Macromedia University of Applied Sciences investigated physiological responses and perceived unpleasantness to uncomfortable sounds. The list includes the sounds of fingernails on chalkboard, the shrill squeaking of styrofoam, and the scraping of a plate with a fork.  

Participants were asked to rate how pleasant or unpleasant various sounds were; this was compared to their physiological response by studying skin conductance, heart rate, and blood pressure. The obtained results were similar to the University of Giessen’s 2022 study of horror movies’ music, where sounds that were rated as more unpleasant led to a more significant physiological response and a higher difference in skin conductance, again showing a connection between noise and the body’s physiological stress responses.

Innovative use of infrasound

Because these discomforting sounds can be identified by viewers, it would be easy enough to just turn the volume down and wait for the spooky scene to pass, steering clear of the scares engineered by a movie’s sound designer. But what if your ears couldn’t hear particular sounds — no matter how creepy? Would they have the same effect, and would it be so easy to avoid?

It’s possible you’ve already experienced the phenomenon of infrasound — a sound so low it is inaudible to human ears — in a horror movie. Director Gaspar Noé confirmed using infrasound in the sound design of horror cinema, notably in the opening of his violent 2002 thriller, Irreversible. 

Infrasound is often described as being felt by listeners, instead of heard, often causing feelings of discomfort. Its particularly low frequencies include noise within a range of 0–20 hertz. For reference, our normal hearing range is around 20 hertz to 20 kilohertz. With this in mind, one can only imagine how horror movies might continue to use infrasound to increase their thrill for audiences.

Although the spookiest season of the year is over, the fear endured by horror fans is almost certain to last in memory, thanks in no small part to the work of the sound designers and composers who helped bring these stories to life. One can only hope that next year’s scares are even bigger and better than ever as research delves deeper into the science behind the creepiest sounds.