Screech...Why You Recoil at the Sound of Fingernails on a Blackboard

(NewsCore) - SCREECH. Shiver. Wince. What makes the sound of fingernails on a chalkboard so incredibly aggravating?

According to a team of German and Austrian scientists, it's a combination of the human ear canal and the power of suggestion, The Local Germany reported.

Researchers Michael Ohler of the Macromedia University for Media and Communication in Cologne and Christoph Reuter from the University of Vienna first determined the sounds of scratching fingernails on a chalkboard and squealing chalk on a slate were the most annoying to people.

They then played them to a group of volunteers, half of whom were told their real origin and half of whom were told they came from contemporary music.

Not surprisingly, those who thought they were art found them less grating, The Local said, suggesting a psychological component to their reaction.

But both groups experienced physiological reactions to the noise, including increased heart rate and sweating, The Local said.

This was apparently due to the pitch frequency of the sounds, between 2,000 and 4,000 hertz, which hits the "sweet spot" at which the human ear is considered to be most sensitive as a result of the anatomy of the ear canal, the scientists said.

The research was presented at the Acoustical Society of America in San Diego, California on Thursday.

Source: The Local Germany