Researchers did not have much idea about how screaming works. In the research, scientists have explored as to how the brain handles a scream. Screams hit straight into the part of the brain that handles fear and separates them from other noises.

Screams target the structure known as amygdale. Study’s lead researcher Luc Arnal, University of Geneva neuroscientist, said, “We knew pretty well what frequencies are used by speech signals and the brain regions involved in speech processing: the auditory cortex and higher order regions such as Broca's area, for instance”.

But it was not known what factors make screams sound so unpleasant. As per the researchers, it is the acoustic quality known as roughness that distinguishes screams from other sounds. Arnal said when compared with normal speech patterns than there is a very slight difference in loudness of just 4 to 5 Hertz.

In the case of screams, the change gap is bigger varying between 30 and 150 Hertz, which indicates the roughness of screams. In a laboratory, the researchers have played recordings from horror movies, YouTube videos and those made by volunteer screams.

After playing the videos, the researchers asked the participants about how scared they were. The researchers found that screams having the highest roughness were the most frightening.

In order to know how these sounds were processed, brain activity was monitored through functional magnetic resonance at the time when the participants listened to screams. It was found that screams increased the fear response in the amygdale.