There are some noises that are so downright horrible, they make the hair stand up on the back of your neck just thinking about them.
For instance, take the sound of nails scraping down a chalkboard. You can hear it in your head now, eeeeeeeee. Why this sound drives us so crazy now has a possible explanation, thanks to two researchers from Austria and Germany.
Musicologists Christoph Reuter and Michael Oehler found that sounds that ranged between 2000 Hz and 4000 Hz, like nails on a chalkboard, are most sensitive to your ears.
"Some frequencies are amplified due to the anatomy of the ear canal," wrote Reuter and Oehler, according to MSNBC's The Body Odd Blog. They recently presented their study at the Acoustical Society of America meeting.
In their study, the pair had two groups of participants listen to either fingernails on a chalkboard or chalk squeaking on a slate. One group was told the sound they'd be hearing, the other group was told they'd be listening to contemporary music. The group warned about the sound reacted more strongly to it than the music group, which suggests the anticipation of an awful noise is part of its unpleasantness.
Both groups had negative physical reactions, including a galvanic skin response, when the skin's electrical activity changes, often triggered by fright.
As horrible as the sound of nails on a chalkboard or squeaky chalk can be, it only came in 16th on a list of the most unpleasant sounds. You don't really need a study, though, to know why the winner, the sound of vomiting, topped the list.