Why Does a Scream Sound So Scary? The Science Behind the Sounds of Halloween
You’re home alone. The lights are off. Then, somewhere behind you...
CREEEEAK.
Your heart jumps before you have even decided whether that sound came from a door, the house settling, or something considerably more interested in eating you.
Halloween is full of sounds designed to make us uncomfortable: footsteps in an empty hallway, a child’s laugh where no child should reasonably be laughing, a low growl, a whisper, the screech of a violin and, of course, the classic blood-curdling scream. But why do certain sounds scare us so effectively?
As it turns out, your auditory system has been preparing for Halloween for a very long time.
A scream is not just a really loud voice
You might assume a scream gets our attention simply because it is loud and high-pitched. There is more going on.
Scientists studying human screams have identified a particular acoustic quality called roughness. In ordinary speech, sound changes at relatively manageable rates. Screams, however, can contain extremely rapid fluctuations in sound intensity. Those fast changes give a scream its harsh, jagged quality and make it particularly difficult to ignore.
Researchers have found that the more acoustic roughness a scream contains, the more frightening listeners tend to perceive it to be. In other words, a scream is remarkably well designed to do exactly what a scream is supposed to do:
GET. YOUR. ATTENTION.
Your brain has an alarm system
Hearing is about much more than understanding words or enjoying music. It is also one of the systems our bodies use to monitor what is happening around us.
Long before doorbells, sirens and smartphone emergency alerts existed, sound could warn us that something important was happening nearby. A cry, a branch snapping, an animal call or someone shouting could all carry information our brains needed to process quickly.
Research into screams suggests that the brain treats certain rough, alarm-like sounds differently from ordinary vocalizations. Those sounds are especially good at capturing our attention and engaging areas of the brain involved in assessing danger and emotional significance.
Which makes sense. If someone nearby screamed, evolution did not exactly reward the person who responded, “Interesting. I’ll investigate that in a few minutes.”
The more useful response was:
“WHAT WAS THAT?”
Horror movies know exactly what they’re doing
Now think about your favorite scary movie. Imagine the villain slowly walking toward the unsuspecting victim.
Now remove the soundtrack.
Suddenly, things may feel considerably less terrifying.
Filmmakers and composers have learned how powerfully sound can manipulate our expectations. Research has even found that some frightening movie music contains acoustic characteristics similar to those found in human screams. That harsh, unstable, almost distressed quality you hear in a horror score may register with your auditory system as something alarm-like.
Then filmmakers add other tricks. A long stretch of quiet makes us listen more closely. A sudden sound creates dramatic contrast. Low rumbles can build a sense of uneasiness, while sounds coming from somewhere we cannot immediately locate force our brains to determine where they originated.
And a perfectly timed shriek can launch an entire bucket of popcorn into the row ahead of you.
Sound designers are not merely decorating the scary scene. Quite often, the sound is creating the scary scene.
Apparently, your ears don’t entirely clock out when you do
Here is perhaps the creepiest part: your brain continues processing some sounds even while you sleep.
Research suggests that the sleeping brain can still distinguish certain features of sounds, including qualities associated with emotionally important or alarm-like noises. That means that even when you are comfortably unconscious, your auditory system is still doing at least a little security work.
Your eyes may be closed and your conscious mind may be elsewhere, but part of your brain is still paying attention to what is happening around you.
Happy Halloween.
Why are mysterious sounds sometimes scarier than what we can see?
Sound has one particularly spooky advantage over vision: you do not have to be facing something to hear it.
Our ears provide information about the world around us from every direction. That is incredibly useful when the sound is a car approaching from behind, someone calling your name from another room, or an alarm warning you of danger.
It is significantly less comforting when the information is:
There is definitely a noise coming from the basement.
Your brain immediately wants answers. Where did it come from? What caused it? Is it getting closer? Should I be concerned?
When we cannot answer those questions, our imagination is more than happy to submit a few suggestions. And our imagination rarely begins with, “Probably nothing. Go peacefully back to sleep.”
Hearing has always been about more than sound
At Hough Ear Institute, we spend a lot of time thinking about hearing. We study what happens when the auditory system is damaged, investigate ways to protect and restore hearing, help people access hearing healthcare, and educate communities about just how extraordinary this complicated system really is.
Usually, we talk about hearing because it allows us to communicate, connect with people we love, enjoy music and participate fully in the world around us.
But hearing has another ancient job. It helps us pay attention. It helps us locate what we cannot see. And sometimes, it tells us very quickly: Something is happening.
So when the lights go out this Halloween and you hear a strange noise somewhere down the hall, remember: your auditory system is doing exactly what it was designed to do.
As for whether you should go investigate the noise?
We’re hearing scientists. You’re on your own with that one.
Happy Halloween from Hough Ear Institute.