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Science

Why Fingernails On a Chalkboard Sound Painful 176

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.'"
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Why Fingernails On a Chalkboard Sound Painful

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  • Taught? (Score:3, Interesting)

    by Hazel Bergeron ( 2015538 ) on Monday October 31, 2011 @04:08PM (#37899466) Journal

    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? (Score:5, Insightful)

      by decipher_saint ( 72686 ) on Monday October 31, 2011 @04:14PM (#37899544)

      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).

      • by X0563511 ( 793323 ) on Monday October 31, 2011 @04:16PM (#37899594) Homepage Journal

        I never found it to be that annoying.

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

        • by Kagura ( 843695 ) on Monday October 31, 2011 @04:43PM (#37899978)

          I never found it to be that annoying.

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

          Exactly the same for me! "Fingernails on a chalkboard" kinds of sounds never bothered me in the slightest. But if I'm the one scraping silverware on a plate, it makes me shudder exactly like other people do when hearing fingernails on a chalkboard! It's weird, maybe my sense of whatever causes the shuddering is slightly "shifted" compared to a normal person.

        • by Mal-2 ( 675116 ) on Monday October 31, 2011 @09:42PM (#37902704) Homepage Journal

          I never found it to be that annoying.

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

          Stravinsky was at a formal dinner of some sort, and asked the diner next to him "do you know how to make a violin section do this?" and scraped his fork across his plate with a horrible screech. When the fellow diner cringed, Stravinsky smiled, and said "I do."

      • by Antony T Curtis ( 89990 ) on Monday October 31, 2011 @04:20PM (#37899638) Homepage Journal

        Communism, like Capitalism: I am not actually aware of anywhere which have attempted to implement these pure concepts.
        Everywhere tends to end up implementing an ad-hoc mish-mash of all three... in varying degrees and proportions.

        • by LordLimecat ( 1103839 ) on Monday October 31, 2011 @10:27PM (#37903100)

          To go completely off-topic:
          Places that historically have been capitalism-based have tended to be generally quite free, and prosperous. Places that have shot for communism have tended to end up as authoritarian, murderous nightmares. The one possible counter-example I can think of, is what China may look like in 20 years-- and mostly because they are shedding so much of the communist vestiges and aiming at hyper-capitalism right now (though they are retaining the authoritarian nature).

          Take that how you want.

        • by hitmark ( 640295 ) on Tuesday November 01, 2011 @06:16AM (#37905330) Journal

          Iraq is the most recent attempt at getting pure capitalism shocked into existence. So far failed attempts are Argentina, Peru and Russia.

    • by JigJag ( 2046772 ) on Monday October 31, 2011 @04:18PM (#37899614)

      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

      • by djdanlib ( 732853 ) on Monday October 31, 2011 @04:28PM (#37899748) Homepage

        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.

        I have seen another distinct entry for your list of reactions. Potheads apparently love the smell. As a non-pothead who grew up in skunk country, it's pretty funny to see people who can't get enough of that vile aroma. Gross!

      • by cruff ( 171569 ) on Monday October 31, 2011 @04:39PM (#37899920)
        Perhaps the odor varies from location to location due to diet or other envrionmental conditions, and possibly by the distance from the point of origin. You should thus perform an experiment for our edification:
        1. Acquire the appropriate eye protection and a sufficient supply of clothing to replace the ruined clothing you will be burning.
        2. Travel to each state and province in North America where skunks are naturally found. Optionally, include locations on other continents.
        3. Start at a distance of 100m from the skunk and provoke it to spray. Record your observations and that of anyone else nearby.
        4. Reduce the distance by half and repeat until either you are located 1m from the skunk or said skunk runs out of spray.
        5. Write a report and post it here so we can evaluate your experience.
      • Re:Taught? (Score:4, Interesting)

        by bws111 ( 1216812 ) on Monday October 31, 2011 @04:43PM (#37899976)

        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.

        • by Zancarius ( 414244 ) on Monday October 31, 2011 @05:12PM (#37900360) Homepage Journal

          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.

          • by exploder ( 196936 ) on Tuesday November 01, 2011 @10:00AM (#37906918) Homepage

            This. One time a skunk sprayed underneath the cabin my family was staying in. It was in the middle of the night, and woke all of us up. We searched the whole place, afraid an appliance was burning out or something It was an awful chemical plastic burning smell that was nothing like the "skunky" whiff you get passing one on the road.

      • by anagama ( 611277 ) <obamaisaneocon@nothingchanged.org> on Monday October 31, 2011 @04:57PM (#37900166) Homepage

        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.

        • by anagama ( 611277 ) <obamaisaneocon@nothingchanged.org> on Monday October 31, 2011 @08:15PM (#37902046) Homepage
          OK, here is the exact quote. It's from page 19, Exploring Puget Sound & British Columbia, Stephen Hilson [google.com]

          June 10, 1792
          Vancouver survey party in this area [points to William Point on Samish Island (*) [google.com]] 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.

    • by skids ( 119237 ) on Monday October 31, 2011 @04:19PM (#37899616) Homepage

      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.

    • by Baloroth ( 2370816 ) on Monday October 31, 2011 @04:25PM (#37899710)
      FTFA:

      The ratings also changed depending on what the listeners thought the sounds were. If they thought a sound came from a musical composition, they rated it as less unpleasant than if they knew it actually was fingernails on a chalkboard. But their skin conductivity changed consistently even when they thought the chalkboard sound was from music and rated it as less unpleasant.

      So yes. They discovered that, even when people said they didn't find it as unpleasant (and thought it was supposed to be music), there was still a physical pain-like reaction in the hearers. Some sounds really are painful.

      Of course, I would probably find it even more painful if you told me it was from a modern musical composition. Cannot stand that crap (I'm talking the orchestral-style musical crap, not the Britney Spears-style musical crap.)

    • by black3d ( 1648913 ) on Monday October 31, 2011 @04:28PM (#37899740)

      Some listeners were told the true source of the sounds, whereas others were told that the sounds were part of contemporary musical compositions.

      The ratings also changed depending on what the listeners thought the sounds were. If they thought a sound came from a musical composition, they rated it as less unpleasant than if they knew it actually was fingernails on a chalkboard. But their skin conductivity changed consistently even when they thought the chalkboard sound was from music and rated it as less unpleasant.

      So naw.. that theory doesn't really hold much water. Personally, I found the chalkboard sound unbearable well before I "knew" I was meant to. More likely it's simply that some folk don't react the same way to that sound (and likely, have their own quirks, completely unrelated). There's a physiological explanation for this which doesn't involve influence, like how some people absolutely can't stand the flavour of gherkin (or pickle, if you prefer), and some love it so much they'll eat my discarded gherkin slices from my burger. :P There's a lot of subtle differences to how individuals perceive sensory input.

      • by black3d ( 1648913 ) on Monday October 31, 2011 @05:03PM (#37900230)

        Also, apologies, I did mean to highlight the second part of that, where their skin consistency changed consistently in either scenario. The part I highlighted agrees with what you said - that there is a cultural attitude that fingernails on a chalkboard is an unpleasant sound. However, this seems to not have any effect on the physiological reaction - that being, the physical reaction is the same in either case.

    • by MobileTatsu-NJG ( 946591 ) on Monday October 31, 2011 @04:47PM (#37900018)

      My cats don't like sounds like that either and I never taught them about the evils of communism.

      Seriously, who modded that up? Somebody who went to a school where the teacher said "Okay class, here's something else you shouldn't like..."

    • by falzer ( 224563 ) on Monday October 31, 2011 @05:00PM (#37900206)

      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.

      • by richlv ( 778496 ) on Monday October 31, 2011 @11:28PM (#37903574)

        oooh. people who object to others wearing socks should be forced to obey any whims anybody on the planet might have. the desire to inflict upon others the annoying feeling of sweaty feet just requires some pushback :>

  • by mrxak ( 727974 ) on Monday October 31, 2011 @04:10PM (#37899488)

    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.

  • by i kan reed ( 749298 ) on Monday October 31, 2011 @04:11PM (#37899490) Homepage Journal

    Since it's a range of doubling frequency, it's one octave. Worst. Scale. Ever.

  • by ackthpt ( 218170 ) on Monday October 31, 2011 @04:11PM (#37899508) Homepage Journal

    You can employ these sounds in your Halloween display!!!

    "I just had that horrible feeling I was in 4th period English again and didn't have my book report done! Arrrggghhh!"

  • by Arlet ( 29997 ) on Monday October 31, 2011 @04:14PM (#37899548)

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

    • by Baloroth ( 2370816 ) on Monday October 31, 2011 @04:31PM (#37899818)

      The researchers suspect that the shape of the human ear canal may be to blame for the pain. Previous studies have shown that the ear canal amplifies certain frequencies, including those in the range of 2000 to 4000 Hz. A loud screech on a chalkboard could be amplified within our ears to painful effect, the researchers propose.

      So, in a sense they did. They didn't prove this is why it is annoying, but it is definitely a possible (and likely) explanation. I personally have noticed those noises appear extremely loud (and hence very annoying.) This may also explain why some people don't find it quite as annoying (as some comments above note): minor variation in ear canal shape would amplify different specific ranges, so certain frequencies could annoy different people more.

    • by bill_mcgonigle ( 4333 ) * on Monday October 31, 2011 @11:44PM (#37903668) Homepage Journal

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

      Some video I watched in high school bio class said that the sounds are coincidentally almost the same waveform as primate danger screeches. Hard-wired aversion.

      Seems plausible.

  • by smoothnorman ( 1670542 ) on Monday October 31, 2011 @04:22PM (#37899658)
    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 [straightdope.com]
    • by bussdriver ( 620565 ) on Monday October 31, 2011 @04:28PM (#37899752)

      We still have chalkboards?

      I thought everybody was getting high off those markers? How about why do those give me headaches?

      • by rossdee ( 243626 ) on Tuesday November 01, 2011 @09:24AM (#37906420)

        When I was a lad at school the teacher would write on a blackboard with chalk. I assume this is refered to these days as a chalkboard - maybe the term blackboard is politically incorrect.

        (I am sure that they would not be allowed to throw chalk at the children who were misbehaving either these days)

      • by exploder ( 196936 ) on Tuesday November 01, 2011 @10:08AM (#37907000) Homepage

        In mathematics departments (in the US, that I know of), there is not a trend toward whiteboards. We like chalk, and are constantly at odds with our IT people who complain about dust in the computers.

        We never asked for the computers, either.

      • by SleazyRidr ( 1563649 ) on Tuesday November 01, 2011 @12:37PM (#37909016)

        The markers give you headaches because they contain a solvent, which is included to make it easier to clean the boards. They're generally based on organic compounds with a low boiling point, so they evaporate quickly, leading to high levels of fumes in the area. When you inhale the fumes they irritate your mucus membranes, leading to a variety of symptoms, including headaches.

    • by b4dc0d3r ( 1268512 ) on Monday October 31, 2011 @05:42PM (#37900718)

      They quote some research which compared two sounds, found them similar, and concluded one was the cause of the other.

      I used to like this idea, but after reading this again it's bunk. They have a hypothesis but nothing to back it up. I like the ear canal idea better, and that leads us the other way around.

      In conclusion, monkey shrieks evolved to match our ear canal design because those who were able to warn others were part of a successful coping strategy. And chalkboards just by chance happen to be similar sounding and unrelated.

    • by Timmmm ( 636430 ) on Monday October 31, 2011 @06:45PM (#37901354)

      Erm, blackboards are still used...

      Also, why do neither of these articles have the sounds to listen to? Seriously, this is as bad as all those articles about imaging that don't have pictures...

  • by unity100 ( 970058 ) on Monday October 31, 2011 @04:30PM (#37899804) Homepage Journal
    It is because it makes me feel as if im doing it, which is very irritating. that dusty blackboard, the nails going against it in the opposite direction.

    notice, the feeling is not so irritating if you do it in the right direction - outwards.
  • by Sarusa ( 104047 ) on Monday October 31, 2011 @04:41PM (#37899950)

    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 [cornell.edu]

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

    • by Falconhell ( 1289630 ) on Monday October 31, 2011 @11:16PM (#37903502) Journal

      There is also the fact that our direction sensing of sound is most sensitive at 2.5KHZ, which also is one of the frequencies
      that we hear very efficiently, I have seen it suggeted due to that region being common in the rustling of leaves and breaking twigs, it was a great asset when avoiding predators in the wild, so we evolved suck sensitivity.

      So much so that Robbie McGrath, AC/DC and Simply Red sound engineer once wrote "2.5K is volume"

    • by Geminii ( 954348 ) on Tuesday November 01, 2011 @07:51AM (#37905706)
      "You have: a hammer..."
    • by davide marney ( 231845 ) * on Tuesday November 01, 2011 @01:13PM (#37909472) Journal

      "And you are designed by millions of years of evolution ..."

      A great example of some of the difficulties of stating evolutionary theory fairly. You can't say that evolution "designed" something, because evolution is a response to external conditions that affect reproduction. It is a weeding-out process. Thus, you'd have to say something like, "Over millions of years of evolution, some external sound source, whose effect on people whose sensitivity to sound was either narrower or broader than today, and which resulted in those people not reproducing at the same rate as today, has resulted in a selection of people who have a painful reaction to the sound of fingernails on chalkboards."

      And if you can "prove" that line of reasoning, you are a better man than I. Evolution, fairly stated, requires a pretty significant level of faith.

  • by Ogive17 ( 691899 ) on Monday October 31, 2011 @04:53PM (#37900096)
    needles into styrofoam. Ugh, makes me cringe just thinking about it.
  • by Anonymous Coward on Monday October 31, 2011 @05:03PM (#37900238)

    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

  • by QuasiSteve ( 2042606 ) on Monday October 31, 2011 @05:08PM (#37900310)

    Fingernails raking against a chalkboard and chalk squeaking against slate were the most unpleasant sounds from a family of recordings, which also included sounds such as Styrofoam squeaks and scraping a plate with a fork.

    Oh scraping a plate with a fork.. *shudder*

    Also unpleasant: rub the smooth ends of two drills together.

    But I have to give kudos to Shad Clark for a sound that is not necessarily cringe-worthy on its own - but by virtue of its associated visual, makes the hairs on my arms stand on end just thinking about it.
    I won't describe it, just let the video in the following URL load...

    http://www.kickstarter.com/projects/shadclark/all-i-think-of-is-you [kickstarter.com] ...then skip to 1:33 and hit play :(

  • by dontmakemethink ( 1186169 ) on Monday October 31, 2011 @05:55PM (#37900868)

    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 [slashdot.org] 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 [usspeaker.com], you might notice they all have spikes around 2-2.5kHz. That is why they suck.

  • by k6mfw ( 1182893 ) on Monday October 31, 2011 @06:19PM (#37901108)

    In a physics class I asked the instructor is there something in our brain that resonates from chalkboard squeals? He thought probably so, kind of like that Tacoma bridge incident. A math teacher used to get excited when the boards were cleaned by custodian, "Yes! We can now break this in" as he would grab a new piece of chalk to use on that dark green board. Then there were some erasers extra wide so not take too long to wipe the board. What about a pocket defense system that blasts high dB levels of this chalkboard sound against muggers? I used to wonder about rigging up something like that.

    Speaking chalkboards, another of those things us old people talk about that 20-somethings ain't got a clue what these are. We now have whiteboards which have their problems (i.e. someone grabs a Sharpie and covers a whiteboard with their discussion. Poor smucks on following meeting get screwed).

  • I can't hear the sound of fingernails on a chalkboard. And no, its not because whiteboards are so much more common now. It's also not from too many loud concerts or anything like that; I couldn't hear fingernails on a chalkboard when I was in elementary school, either (I did it once to get my classmates' attention and thought I was doing it wrong since I didn't hear anything).

    Are there many others who can't hear it?
  • by flimflammer ( 956759 ) on Monday October 31, 2011 @09:17PM (#37902506)

    As a kid nothing could phase me. I'd laugh when someone would try it and I'd see everyone freaking out. But when I turned around 20 several years ago that all changed and I've become super sensitive. It's not even just fingernails on chalk boards that get me, it's a wide assortment of things.

  • by GeneralEmergency ( 240687 ) on Tuesday November 01, 2011 @02:44AM (#37904522) Journal

    .

    Ah, yes. Very familiar with that range.

    The "Ex-Wife" frequencies.

    .

  • by Phoenix ( 2762 ) on Tuesday November 01, 2011 @07:36AM (#37905654)

    I can not remember which Science Show I was watching at the time but I learned that it was the lower frequencies at least in the early 2000's.

    While I'm not sure if they mentioned the specific 2k-4k range, they had broken the noise into low, mid, and high frequencies and did a test with people listening to the noise. While some did flinch at the higher frequencies, most reacted to the lower range.

    So unless they took almost a decade to isolate the specific frequency range...is this really new?

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