Reason why we have a chill when hearing a scream

When a neck-broken ghost named Sadako crawls out of a TV in the Japanese movie “Ring,” people cannot help but screaming ‘Ugh!’ Screaming is like a sound effect for a horror movie generated by audiences. People have a chill when hearing others scream. Even a scream coming from afar is audible.

An American research team has recently analyzed a scream acoustically and published the article on an international journal “Current Biology” on Wednesday. Research team led by Professor David Poeppel at the language comprehension lab of New York University has extracted and analyzed screams from horror movies and videos uploaded on the YouTube. The research team has found the number of vibrations makes a scream audible.

The number of vibrations when a person talks in a general occasion is consistent ranging from 4 to 5 Hz. However, the number of vibrations in a scream is between 30 and 150 Hz. The sound wave of a scream changes rapidly generating a sharp sound. It is similar to the reason why the sound of car horns is audible even on a noisy road.

In the experiment, researchers let 19 subjects hear sounds of a scream and a recorded voice reading “Oh my god, help me.” The research team also scanned subjects’ brains with fMRI. When hearing a scream, the auditory cortex and the amygdala, which feels fear, were noticeably activated in a subject’s brain. When hearing a voice calling for help, only the auditory cortex responded.

The research team artificially increased the number of vibrations which were captured from a conversation or singing a song to make it sound like a scream. When the subjects heard the sound, the part of brain that feels fear was strongly stimulated. “The amygdala is a brain part that engages in emotion or feeling generated on the spot. As the amygdala is sensitive to a sharp noise, people feel fear immediately when hearing a scream,” said Professor Poeppel.

“The wavelength of sound wave is short in case like a scream, in which high-pitched sound is loud. Sound with short wavelengths spreads well to the surroundings,” said Professor Lee Seok-pil of the Media Software Department at Sangmyung University.