科学美国人60秒:What All the Screaming Is about

Got your attention? Thought so. But what is it about a piercing shriek that really turns our heads? It’s what it does to our brains. The acoustical properties of the human scream poke at the neural circuits that control fear. That’s according to a study in the journal Current Biology. [Luc H. Arnal et al, Human Screams Occupy a Privileged Niche in the Communication Soundscape]

Our every waking moment is filled with noise, from planes flying overhead to various creatures scrambling underfoot. But a heartfelt cry can cut through all that. So what’s so special about the sound of a screech?

To find out, researchers prepared a sampler of screams from YouTube videos, popular films and excited volunteers. [Wilhelm Scream sound] If that screech sounded familiar, that’s because it’s the famous Wilhelm Scream, a stock sound effect heard in everything from Bugs Bunny to Star Wars.

The scientists analyzed the acoustical characteristics of the various screams. And they found these alarming sounds are not only loud, they’re particularly rough. That is, they rapidly change in frequency. Normal speech is relatively smooth, with frequencies ranging only between four and five Hertz, or cycles per second. But a shriek can swiftly fluctuate between 30 and 150 Hertz—a range that can make your hair stand on end.

When the researchers asked people to rate how frightening screams were, they found that more roughness meant more terrifying.  And increasing roughness of the sound corresponded to greater activation of the fear center of the brain.

Only one other noise scored as high as screams in terms of roughness [car alarm sound]. Which, ironically, is enough to make you [scream sound].

—Karen Hopkin