Why does hearing sounds like nails on a chalkboard and also imagining them, create such an irritating sensation?
In: Biology
People are designed to hear speech, people having conversations, especially well. Because you are so sensitive to the sound of people’s voices you are also really sensitive to any noise at the same frequency. Nails on a chalk board happen to be at the same frequency as people talking, but sound nothing like it. So it really hurts your brain to try and process it, but equally because you are so sensitive to it, you can’t ignore it.
Imagine it’s like the ‘[uncanny valley](https://en.m.wikipedia.org/wiki/Uncanny_valley)’ but for sound.
I remember reading the theory that it could be an evolutionary reaction to our primate ancestors’ giant bird predators.
https://www.sciencedaily.com/releases/2006/08/060830005634.htm
(Edit: apparently that wasn’t clear: the sound of a chalkboard or plate scratch was posited to be similar to the screech of giant primate-eating raptors of our primordial ancestors)
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Researchers have found the “nails on a chalkboard” to have the frequency range of between 2,000 and 4,000 Hz — which is the same range as human speech. This ear-splitting noise has the same frequency as that of a human scream, indicating that these sounds are tied to survival. Amazingly, when these frequencies were filtered out and the sound replayed, people have no trouble listening to the sound.
Edit: guys apparently I have my frequency hertzs wrong.
Edit2: ok found it. [“Screams also have energy in the same frequency band, but its concentration is less.”](https://www.nbcnews.com/healthmain/screech-sounds-which-are-worse-nails-chalkboard-1C6541925)
Side question, does the irritation have something to do with certain sound frequencies?
I ask that because when I was younger those sounds ( like nails on a chalk board, or my cat scraping its claws on the bottom of the plastic litter tray) didn’t bother me. As I have gotten older and obviously lost hearing at certain frequencies, I can’t stand it.
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