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This is the frequency/intensity that sets my teeth on edge.

Does anybody know what frequency (roughly) it is? I am guessing it is near the top of normal human hearing, 20kHZ, but I'm not sure if that's why it affects me.

I am sure the same frequency is played on some of the music I listen to, but somehow, it does not make me wince.

There is a related question here, with no answer Scratching on a Blackboard, but I just want a frequency value.

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  • $\begingroup$ It contains multiple frequencies, so it is not one specific frequency. $\endgroup$ – fibonatic Jul 26 '16 at 20:08
  • $\begingroup$ @fibonatic I didn't think of that, I wonder are they close together, or harmonics, maybe it's that mix that causes the effect. Thanks $\endgroup$ – user108787 Jul 26 '16 at 20:13
  • $\begingroup$ I have an app on my phone called "n-Track Tuner" that shows the spectrum of frequencies of a sound. Quite fun to play with. I don't have a blackboard right here, so I can't give you an answer, though. $\endgroup$ – pela Jul 26 '16 at 21:02
  • $\begingroup$ @pela ok, I downloaded the app, just going out to get earplugs before experiment. Thanks for the tip $\endgroup$ – user108787 Jul 27 '16 at 17:26
  • $\begingroup$ Ha ha good idea :) $\endgroup$ – pela Jul 27 '16 at 19:45
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From http://www.livescience.com/16967-fingernails-chalkboard-painful.html:

Interestingly, the most painful frequencies were not the highest or lowest, but instead were those that were between 2,000 and 4,000 Hz. The human ear is most sensitive to sounds that fall in this frequency range, said Michael Oehler, professor of media and music management at the University of Cologne in Germany, who was one of the researchers in the study.

No one knows all of the reasons why that sound is so painful to listen to, but some theorize that we evolved ear canals to amplify human speech as much as possible, and that sounds like this happen to have large portions of their energy in that frequency band.

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  • $\begingroup$ Thanks very much, if I was really cruel, I would have included an mp3 of the sound in the question. $\endgroup$ – user108787 Jul 26 '16 at 20:37
  • $\begingroup$ Personally, I think there's something very psychological about it. I find myself to be very unaffected by the sound, but have a very musically inclined ear. This seems to suggest that there's something in our brain that's key to understanding the annoyance of the sound. $\endgroup$ – Cort Ammon Jul 26 '16 at 20:40
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In addition to the other answer by Cort Ammon, I have heard of other psychophysical/evolutionary explanation:

The frequency distribution of that sound closely corresponds to the frequency of a crying baby, which has been shown to drive people crazy when exposed to it for a short amount of time (we are genetically predisposed to get distressed by such a call). In this case the specific frequency distribution of nails in a chalkboard is better as stimulating those neural pathways than the stimulation produced by the original sound.

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  • $\begingroup$ I've heard both sounds a lot and do not believe they are similar. $\endgroup$ – WGroleau Jul 27 '16 at 5:24
  • $\begingroup$ you cannot trust perception livescience.com/16967-fingernails-chalkboard-painful.html $\endgroup$ – Wolphram jonny Jul 27 '16 at 15:38
  • $\begingroup$ You cannot trust casual reading. I do not find that article convincing--like so many studies, too few independent variables and dependent variables that were expected to support the hypothesis were ignored when they didn't. But in any case, the article does not claim that a crying baby sounds like nails on a chalkboard—it says that both sounds contain energies in the 2-4 kHz band. And they take a psychological reaction to the modified sound & assume the same reaction will occur with the unmodified sound. In spite of all that, the filtering suggestion does merit another experiment. $\endgroup$ – WGroleau Jul 28 '16 at 0:56
  • $\begingroup$ sure, I agree it is only an idea, but is an educated guess as opposed to a random guess, see also en.wikipedia.org/wiki/Supernormal_stimulus $\endgroup$ – Wolphram jonny Jul 28 '16 at 1:36

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