Why Is 'Fingernails On A Chalkboard' The Worst Sound Ever?

Most of us cannot STAND the sound of fingernails down a chalkboard and we've always wondered why!

It's a similar reaction to when someone drags their cutlery across a plate, and as with many things, the answer is science. Researchers at the University of Cologne in Austria have answered this very important question.

It's your ears' fault:

"Sounds in [a certain] range are amplified due to the anatomy of the ear canal; they are literally louder to us than other sounds are."

Basically the shape of the ear amplifies the sound of fingernails running across a chalkboard, cutlery on a plate, and a nail file on your overgrown claws. 

Cheers nature!

Explaining the situation further, the scientists said that the ear "may have evolved to amplify frequencies that are important for communication...[which] could have been advantageous for survival, allowing people to come to the rescue of their screaming infants quicker, and thus improve their offspring's chance of survival, or coordinate more effectively during a hunt."

So when we hear the awful sounds of nails scraping on a chalkboard or a knife across a plate, we react in a hugely dramatic way because the noise is hitting "right in the sweet spot of human hearing," TIFO reported.

Source.