Why does the sound of scratching the blackboard with nails make people tremble?

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In this paper, the authorization is reproduced from: tadpole five-wire spectrum (ID:kedo2011). Compilation: clear sky flying swallow.

If you are no different from ordinary people, you may not be able to stand the sound of fingernails scratching through the blackboard, which feels like.

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Since most people are extremely annoyed with this kind of ear-sharp sound, it is not surprising that research on why this kind of sound can stimulate a similar instinctive response has attracted the attention of many scientists.

Overall, research has shown that this "blue-skinned mushroom" noise has the same frequency as baby crying and human screaming, indicating that these sounds are associated with "survival." For example, people think that this frequency of sound can make people cry faster to cry the baby, extending the life of the baby.

A study shows that our aversion to this harsh sound is due to the shape and perception of our ear canal.

Participants in the study assessed different annoying noises improperly. These sounds include the sound of chopsticks scraping plates, the sound of foam polystyrene friction, and so on. The most uncomfortable sounds rated by the participants were the sound of fingers scraping through the blackboard and the sound of chalk scraping through rocks.

The researchers then created variants of the sounds by adjusting the frequency range of the two sounds and removing harmonic parts (or other harmonious tones). They told 50 percent of the subjects the true source of the sound, while the other half were told that the sound came from several pieces of contemporary music. In the end, they played the relevant sounds to the two groups of participants and monitored the subjects' heart rate, blood and skin conductivity and other stress indicators at the same time.

They found that this annoying sound significantly changed the conductivity of the listener's skin. This suggests that the sound does cause a major physical stress response.

Michelle Earler, professor at the School of Media and Music Management, Department of Applied Science, University of McComedia, Germany, said:

"The most painful frequencies are not the lowest or highest frequencies, but those between 2000 and 4000 Hz. Human ears are most sensitive to the frequency of sound in this range."

Professor Earler points out that the shape of the human ear canal may evolve to amplify the frequency of certain sounds related to communication and survival. Ear canal evolution is good for humans, but it also has side effects: it is extremely painful when the finger scratches through the blackboard and is magnified. "but it's really just a theory, and now the only thing we can be sure of is that we've found a source of this unpleasant frequency."

In the study, listeners who were told that the sound came from music thought the sound was more comfortable, Professor Earler said. (but this does not deceive their bodies because the skin conductivity of both groups of listeners in the experiment changed the same.) This suggests that if we don't have very annoying and negative presuppositions about this sound, it may not be so annoying.

The choice of the brain

Another study published in the Journal of Neurology in 2012 revealed changes in the human brain when people hear such sharp sounds. Studies have shown that the sound of a finger across the blackboard causes a stronger exchange of hearing and affection in the brain.

In this study, 13 subjects listened to a total of 74 sounds, including the sound of nails across the blackboard and the noise of power tools, and scored the pleasure of these sounds based on their feelings. The researchers used functional magnetic resonance imaging to determine how the subject's brain responded to these sounds.

When the subjects heard an unpleasant sound, the auditory cortex that processed the sound and the almond area that dealt with negative emotions interacted.

"this seems to confirm a very primitive view that when you hear unpleasant sounds, the almond body of the brain may transmit a distress signal to the auditory cortex," said Sekubeid Kurma, a member of the Newcastle University research team. "this seems to confirm a very primitive view that when you hear unpleasant sounds, the almond body of the brain may transmit a distress signal to the auditory cortex."

In addition, the researchers say that the more dissatisfaction this sound brings, the more active the activity in these two regions of the brain. Based on the subject's ratings, the researchers found that the most unpleasant sounds included the sound of a knife across the bottle, the sound of a fork across the glass, and the sound of chalk across the blackboard. The best sounds to listen to include water, thunder and children's laughter.

Funny Nobel Prize

In 2006, a study that investigated all the sharp voices received a funny Nobel Prize from the Impossible Research Association. The study was published in Perception and Psychophysics in 1986, in which scientists recorded the sound of gardening tools scratching the blackboard. Next, the researchers constantly adjusted the frequency of the sound and removed the high, medium and low frequencies in different recordings.

When the researchers played the adjusted sound to the volunteers, they found that removing high-frequency sounds did not make the whole sound more enjoyable. Instead, they learned in medical journals that deleting intermediate and low frequency sounds can make the whole sound more moving.

In addition, the researchers found that the gorilla-warning cry and the sound of fingers crossing the blackboard have similarities. Perhaps people have an unconscious reflection of such sounds, because such sounds and warning signals have mysterious similarities, the researchers told Medical Health.

Nails scratches blackboards voices tremors.

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