Why Fingernails On a Chalkboard Sound Painful

sciencehabit writes "Some sounds are excruciating. Take fingernails squeaking on a chalkboard. The noise makes many people shudder, but researchers never knew exactly why. A new study finds that there are two factors at work: the knowledge of where the sound is coming from and the unfortunate design of our ear canals. 'The offending frequencies were in the range of 2000 to 4000 Hz. Removing those made the sounds much easier to listen to. Deleting the tonal parts of the sound entirely also made listeners perceive the sound as more pleasant, whereas removing other frequencies or the noisy, scraping parts of the sound made little difference.'"

Comments

Taught?

[Hazel Bergeron]

Did they test with people who haven't been culturally informed that fingernails on a chalkboard should sound annoying?

From chalk to communism, there are so many, "Why do people find blah disagreeable?" which seem to come down to, "Because that's what mother and the TV say."

Re:Taught?

[decipher_saint]

Dammit no. I remember being a child and hearing that sound and cringing then finding out AFTER that I wasn't alone.

Some things just plain old suck (like fingernails on a chalkboard and communism).

Re:Taught?

[X0563511]

I never found it to be that annoying.

Now, silverware scratching on a plate? Gives me the shudders.

Re:Taught?

[JigJag]

I agree with you. Fingernails on chalkboard never bothered me and they still don't. I have excellent audio reception btw so it's not a question of being tone-deaf. I hear the sounds but my skin doesn't crawl up.

On a related note, I moved from a place with no skunks to a place teeming with them. To the locals, the odour is unbearable and they have like a flight-response to it. Personally, I don't abhor the smell; It's akin to "burning rubber". When my mother visited, it reminded her of the smell of "roasting coffee". We weren't raised to despise that smell, and we don't when confronted to it. That being said, I never have been sprayed or anything like that. I am talking about the far-off whiff you get in you're downwind from a skunk.

JigJag

Re:Taught?

[skids]

More importantly, do they control for whether or not test subjects have actually tried to make the noise by themselves running their fingernails down a chalkboard.

For me the noise meant nothing until it was linked with the disturbing feeling of chalk building up under my nails as they vibrate painfully.

Re:Taught?

[bws111]

Isn't that just learning? You have not yet directly experienced skunk spray, so it doesn't have the same effect on you as someone who has experienced it. The area I have always lived in has a lot of skunks. Like you, the smell never bothered me all that much. Then one day our cat got sprayed, and before we knew it he was in the house. Now I absolutely can not stand that smell, no matter how far off it is.

Re:Taught?

[anagama]

I have this great book of marine charts for the Puget Sound which places historical anecdotes in place context.

There is one entry from early European explorers, which indicates that one of the men chased down a skunk having never seen such an animal before. It continues to note that the stench was unbearable, that no amount of boiling would remove it from the clothes, and that in the end, the skunk hunters were forced to destroy their clothing.

I'd quote it exactly but its on my boat. Anyway, close contact with pure skunk essence is not at all like a whiff on the wind -- it really is unbearable even to people who have never even heard about skunks, let alone people like you who are aware of them but have not experienced their power at close range.

Re:Taught?

[falzer]

It would get very tiresome for everyone to have to explain from axioms and first principles every opinion they held, even if they did reflect upon and study them.
Alternately, do you think people who agree with you on whatever subject have also been "culturally informed" that way?

I am, of course, not talking about capitalism, communism, chalk, or cottonballs, but wearing socks with sandals.

Re:Taught?

[Zancarius]

Isn't that just learning? You have not yet directly experienced skunk spray, so it doesn't have the same effect on you as someone who has experienced it. The area I have always lived in has a lot of skunks. Like you, the smell never bothered me all that much. Then one day our cat got sprayed, and before we knew it he was in the house. Now I absolutely can not stand that smell, no matter how far off it is.

People who've never lived in areas with a lot of skunks seldom appreciate just how potent and horrendous fresh spray is. It doesn't smell anything like the odor of a far off skunk. I had a cat that got skunked once and did the exact same thing. I've heard fresh skunk spray described as an acrid mix of burning onion, garlic, and tire rubber left on the stove to char, and that seems pretty accurate.

Re:Taught?

[Seng]

Microfiber cotton "terrycloth" wipes do that to me - the kind that kind of snag your fingertips no matter how smooth or clean your fingers seem to be.

Re:Taught?

[BluBrick]

Are you absolutely sure you were never taught that? There are many ways of being taught. Perhaps it was not a conscious lesson, and perhaps it was not even the intent of the lesson. Infants have a tendency to experiment with things that make new sounds. If that new sound is "unpleasant" enough, you can be certain that any nearby adults will exhibit some sort of reaction. That reaction could be irritation, visibly blocking the ears, or even taking away the object that causes the sound. From such a reaction, the infant is bound to learn something from the experience.

Or perhaps the handling of polystyrene sounds very similar to a sound to which you have a learned response.

Re:Taught?

[anagama]

OK, here is the exact quote. It's from page 19, Exploring Puget Sound & British Columbia, Stephen Hilson

June 10, 1792
Vancouver survey party in this area [points to William Point on Samish Island (*)] Puget relates ... "An animal called a Skunk was run down by one of the marines after Dark & the intolerable stench it created absolutely awakened us in the tent. The Smell is to bad for a Description ... The Man's Cloaths were afterwards so offensive that notwithstanding boiling, they still retained the Stench of the Animal & in the Next Expedition others were given him on Condition that those that retained the Smell should be thrown away & happy he was to comply with it.

[odd spellings and capitalizations in the original]

(*) Williams Point is on the upper side of the middle hump just to the left of the B marker. I can't move the marker off the road.

Just thinking about it

[mrxak]

There's certainly a psychological component. Just thinking about that noise and making the clawing/scraping motion with my hand, right now, made me react as I would hearing it for real.

Re:Just thinking about it

[Baloroth]

They also tested Styrofoam squeaks and forks scraping on plates. You are welcome :)

They still haven't explained it

[Arlet]

They've only narrowed down the class of sounds, but not why we would find those sounds so annoying.

The Straight Dope ...did it

[smoothnorman]

and in 1986 no less (back when "chalkboard" still had some meaning): http://www.straightdope.com/columns/read/540/why-is-the-sound-of-fingernails-scraping-a-blackboard-so-annoying

Re:The Straight Dope ...did it

[EXrider]

Most of the schools around here have Smartboards now... and the average kids that are graduating from said schools around here are still dumb as shit, so much for Smartboards.

That's Baby Crying Frequency

[Sarusa]

Baby crying has a wide variation, and the fundamental frequency is (depending on who you ask) somewhere around 500Hz, but you get strong harmonics and nonlinears up in the 3Khz area. The non-linears are a strong part of the annoyance too. See for example http://ergo.human.cornell.edu/studentdownloads/DEA3500pdfs/hearing.pdf

And you are designed by millions of years of evolution to find that so annoying you will do anything to make it stop.

Re:My wife's voice

[MobileTatsu-NJG]

Yeah, inflatable plastic makes a balloon-like squeal when punctured.

Worse than fingernails

[Anonymous Coward]

My high school music teacher taught me how to make a stick of chalk squeal on a chalkboard at will.

Hold a fresh piece between your first two fingers and your thumb lightly, with the other end resting against the middle of your palm. hold the tip against the board with a sharp downward angle about the same as a backslash \, and draw a line downward. Don't press too hard or you'll dampen the resonance and get nothing. When you get the hang of it it's very easy to produce a head-splitting screech above 100dB

A little late on this one

[dontmakemethink]

You don't need an audiology experiment to figure this out. Harvey Fletcher and W. A. Munson established the lab work back in 1933, resulting in the Fletcher-Munson Curve which illustrates how the sensitivity of the human ear varies at different frequency ranges and volume levels, and is most sensitive in the 2-6kHz range. It's fair to assume this range is more sensitive since it is the hardest range for predators to keep silent while stalking prey, i.e. a twig snapping.

It is believed mankind has pre-historic rodents to thank for their advanced auditory system, which developed during the 65 million year period where mammals and dinosaurs co-existed. During this time there was low oxygen content in the air, so mammals had to maintain high respiratory rates, making them easy prey for the much larger dinosaurs, whose respiratory system involved hollow bones to transport air directly throughout their bodies rather than just lungs to deliver oxygen to the bloodstream. (Birds benefited from the hollow bones to fly, but only use lungs for respiration now that oxygen levels are up.) Mammals had to forage at night and depended almost entirely on their auditory systems for defense. 65 million years of that is likely the only reason we can discern music, much less appreciate it.

As a sound engineer I can attest that the 2-6kHz range is of special significance when putting a mix together. It's usually actually more important that the 2-6kHz range of each voice or instrument be balanced against each other than each voice or instrument be of even frequency response themselves. If something is dominant in that range, it dominates the listener's attention every time. If something has a sharp spike in that range, meaning a very narrow frequency band, it will not be pleasant to the ear. If you check out the frequency response graphs of the cheaper guitar speakers by clicking on the options here, you might notice they all have spikes around 2-2.5kHz. That is why they suck.

Re:My wife's voice

[uncqual]

How is the AC's comment sexist?

It appears that AC is married to someone with a harsh voice. The AC didn't claim that all women, or even all wives, have harsh voices. AC just claimed one person who AC likely spends a lot of time with has a harsh voice.

Although AC could have said "$WIFE_NAME's voice is the only sound more harsh...", that would not have conveyed that AC likely spent a lot of time with that person. For example, if AC had said "Jane's voice is the only sound more harsh...", for all we know 'Jane' could be a checker at the local Walmart and since, presumably, AC doesn't spend that much time with a particular checker at Walmart, the message would have reduced significance.

AC could have used the word spouse instead, but that's rather unnatural and unusual as most people refer to their 'wife' or 'husband' rather than their 'spouse' in normal conversation.

Not all observations or criticisms aimed at anyone but a straight white middle aged able-bodied mail is "racist" or "sexist" or "$GROUPphobic".

Re:My wife's voice

[syousef]

It appears that AC is married to someone with a harsh voice. The AC didn't claim that all women, or even all wives, have harsh voices. AC just claimed one person who AC likely spends a lot of time with has a harsh voice.

For some reason, it almost always happens to be wives rather than husbands that are referred to as having harsh, screetching voices. Odd that. Heaven forbid anyone suggest this might be due to sexism, though!

The human male voice tends to be deeper than the female voice. This has to do with physiology. So referring to husbands as having shrill irritating voices does not ring true. Stereotypes tend to take a truth and exaggerate it - the truth makes it recognisable. Heaven forbid reality get in the way of political correctness.

There are plenty of anti-male stereotypes - just watch an episode of an American sitcom like say Everybody Loves Raymond for example. He's obtuse, lazy and incompetent. His wife is whiny over-emotional and nags. That doesn't make anyone laughing at the gags a sexist monster who wants to put down the opposite sex.