Why is the sound of fingernails scraping a chalkboard, or the sound of Styrofoam rubbing together so painful to listen to?

September 5, 2007 1:55 AM

Why is the sound of fingernails scraping a chalkboard, or the sound of Styrofoam rubbing together so painful to listen to?
posted by friedbeef to science & nature (15 comments total)

It seems to be something that varies between individuals - neither sound bothers me in the least.
posted by ellF at 3:55 AM on September 5, 2007

Regarding fingernails on a chalkboard...

This Q&A is from the scraper's perspective: Link

This Q&A is from the non-scraper's perspective: Link

Honestly, I have never heard of the styrofoam rubbing thing being an issue.
posted by TheAnswer at 4:02 AM on September 5, 2007

Maybe some people's ears are more sensitive to higher pitches? For example, I can always hear when a TV has been left on standby, even in another room, but I can't hear bass at all. Below a certain point, it all just sounds like quiet thunder. Sonic cat scarers drive me mad.

So I guess some people's ears are just tuned in to higher frequencies, or maybe they can't process the higher frequencies as well, and the "force" of the noise is more than they can stand.
posted by Solomon at 4:23 AM on September 5, 2007

Did you Google? The Straight Dope result is the first answer.

Apparently, someone won the Ig Nobel Prize asking this very question. From the article:

“To our surprise, the removal of the high frequencies didn’t reduce the aversive qualities of the sound, but removing the middle frequencies of the sound did,” he said.

Intrigued by this finding, Blake set about examining the sound waves associated with other vocalizations, including primate distress calls.

“It turns out the sound waves associated with primate warning cries, particularly chimpanzee warning cries, are remarkably similar in appearance to the aversive, middle frequency sound waves produced by fingernails on a chalkboard,” he said. “When you hear those cries, they are eerily similar to fingernails on a chalkboard.

“Our speculation was that the reason the sound of fingernails on a chalkboard have an almost universal aversive quality is that it triggers in us an unconscious, automatic reflex that we’re hearing a warning cry.”

posted by youarenothere at 5:43 AM on September 5, 2007 [12 favorites has favorites]

For me, it's not the sound itself that bothers me but the memory of how it felt the one time I actually did scrape my own fingernails across a blackboard. That was an awful feeling and I apparently associate the sound with the bad feeling. Try it.
posted by Hobgoblin at 6:28 AM on September 5, 2007

Honestly, I have never heard of the styrofoam rubbing thing being an issue.

Well, count me in for one data point. I can't stand that sound, or the sound of crinkling plastic/cellophane.
posted by cabingirl at 6:37 AM on September 5, 2007

Honestly, I have never heard of the styrofoam rubbing thing being an issue.

This absolutely cripples me. It's horrible. Every time I unpack a new computer or other appliance I have to do it very carefully. Even the thought of it is enough to send shivers up my spine.

The worst thing about it is nobody ever realizes how bad it is for me so if I ask someone to stop they think it's funny and they keep doing it to bug me. But it's not funny at all, it's actually painful and turns me into a quivering blog of jello. I can't explain why.

Oddly enough, fingernails on a chalkboard doesn't bother me at all.

I heard one theory that the high frequency reminded us of the cry of predators from back when we were lower on the food chain, but I don't know if I believe that.
posted by bondcliff at 6:55 AM on September 5, 2007

None of the linked answers really explain it, except to pin it down to the middle frequencies. My theory is that it's dissonance, like you hear when you listen to the violins in a seventh grade orchestra composed of inexperienced players. That violin sound isn't always quite as painful as the fingernail scraping, but there's something very disconcerting about it. You get similar dissonance with lots of other things scraping, some more bothersome than others. The fingernails on the blackboard is usually described as "spine-tingling" -- is it possible that the particular dissonant tones in that sound coincide or resonate specifically with certain nerve pulses that would cause those sensations? This short piece (taking off from that orchestral dissonance) explains how sound frequencies are translated to hairlike structures in the inner ear that are tuned to specific frequencies. A dissonant sound, composed of many frequencies close together like the fingernails on the blackboard or the 7th grade violin section, will excite a whole swatch of these hairs, probably throwing the brain a bit of sensory overload and causing the reaction in question.
posted by beagle at 8:22 AM on September 5, 2007

I can't stand styrofoam against cardboard.
posted by Camel of Space at 9:16 AM on September 5, 2007

It's bad, but it's not the worst sound in the world.
posted by clh at 10:28 AM on September 5, 2007

For me, it's not the sound, but the pressure being used to make it happen. Neither of those things really bother me, but oh-holy-hell, I can't handle having anyone touch my cuticles, especially the pushing back thing they do in a manicure. It doesn't hurt, but I lose track of what I'm doing and my stomach roils. Anyone near me clicking their fingernails together is no good either - i hear it and then feel the pressure somehow, even if they're not touching me, and then I leave the room. Those are just a couple of my examples, but they're much worse than the others.

[SlightDerail] I'd be interested in finding out ways to handle sounds or issues like these without interrupting your train of thought, if anyone has any ideas.
posted by mitzyjalapeno at 11:51 AM on September 5, 2007

mitzy: start with very very light pressure and gradually increase. Would that work to desensitize?

Same with the rubbing/scratching sounds, start soft and increase pressure. Pretty soon you'll be chewing foil.
posted by artdrectr at 12:23 PM on September 5, 2007

For me, when I was young, it was the scraping of the spaghetti out of the pot my mother cooked it in. She used a regular kitchen fork. Far worse than any chalkboard, the sound of that stopped me in my tracks and as I got older, she scraped just to watch me cringe. (It took longer to type this than it should have. I had to stop three or four times just from thinking about it.)
posted by bach at 12:25 PM on September 5, 2007

I don't recall hearing anything which could match the horror of a recording of the cries of babies with severe congenital birth defects I heard a few snippets of on the radio years ago, but I think for me the fingernails on chalkboards business has more to do with re-experiencing the awful texture of chalk and the feeling of accidentally scraping it across boards myself a few times. When I hear that sound, I mainly feel the distress of it in my hands. The same is true of the styrofoam packing pasta
posted by jamjam at 1:22 PM on September 5, 2007

I hope this isn't too off-topic: There are other horrors analogous to the above-mentioned sounds. This morning a harmless but large insect in my bathroom basically sent me off the rails, and I thought immediately of this thread. No logic to it at all. It must be a similar reaction.
posted by JimN2TAW at 8:25 AM on September 6, 2007