The sound of fingernails scraping across a chalkboard is pretty much the ne plus ultra of unbearable noises. Just thinking about it is enough to make your skin crawl and your hair stand on end.
As Hank Green explains in this episode of SciShow, there have actually been a number of studies into why humans hate this kind of sound, which also includes things like a fork scratching on a plate or tires squealing.
it's been found that the most universally-despised sounds have one thing in common: their frequency.
Specifically, they all fall in the range of 2,000-5,000 hertz (cycles per second).
There are a number of theories as to why this particular frequency range stabs our brain. Some think it might be an evolutionary adaptation left over from our ancestors, as it sounds similar to monkeys screaming.
Others suggest that the the shape of our ears preferentially amplifies sounds in this frequency range, making them more intense. One study found that people who hear these noises show heightened activity in brain areas associated with anger, though it's not clear if that's why we started hating the sound, or if we learned to have an aversion to them over time.
For such a seemingly simple thing, the science behind why everybody hates these noises is really cool.
Check out the video to learn more!
(And don't worry, he doesn't actually play the awful sounds in the video!)
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