A new study by musicologists in Europe suggests that the shape of our ear canals, as well as our own perceptions, is to blame for our distaste in such shrill sounds.
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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.
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In any case, Oehler and his colleague Christoph Reuter of the University of Vienna found that our hatred of chalkboard screeches is not solely based in physiology; there are some psychological factors at work, too. Overall, the listeners in the study rated a sound as more pleasant if they thought it was pulled from a musical composition (though this didn't fool their bodies, as participants in both study groups expressed the same changes in skin conductivity). The implication, then, is that chalkboard screeches may not irk us so much if we didn't already think the sound is impossibly annoying.
Why Do Fingernails on a Chalkboard Make Us Cringe?