Interesting : Why is the sound of fingernails on a blackboard so annoying?

Why is the sound of fingernails on a blackboard so annoying?

Certain high-pitch frequencies, such as those created by dentist drills or two pieces of Styrofoam scraping together, tend to universally antagonize. On the other hand, particular notes played together sound harmonically "correct." There's no clear-cut reason why. Cecil Adams of the venerable The Straight Dope cites a scientific study in a journal called Perception and Psychophysics that equates the frequency of a harsh scraping sound with that of the distress calls used by Macaque monkeys. The theory is that our simian ancestors employed a similar pitch to warn each other of predators, and we still respond to it. This seems to be the accepted wisdom on the subject -- it's the frequency, Kenneth. Most alarm cries from animals involve high, screeching sounds. Psychologist Barry Beyerstein on Science Canada seems to think the answer has something to do with nerve endings in your fingers, but if you can understand his response, more power to you.