Why is the sound of nails scraping on a blackboard so annoying to people?

(ORDO NEWS) — Many sounds can be annoying. But why is this happening? It turns out that the answer to this question is closely related to the sound of wild animals gnawing at human bones. It sounds terrible, but scientists, through a number of studies, have found a scientific basis for this. Details are in the article.

There are many strange sounds in life that drive us crazy. For example, the sound of nails scraping on a chalkboard sounds very unpleasant, but why is this happening?

To answer this question, you need to go back far, far into the past. Then our ancestors lived in the wild, and they had to not only look for food in order to feed themselves, but also always be on guard, remembering that there may be predatory animals nearby. Over time, humans instinctively became extremely sensitive to sounds such as when large predators gnaw through the skull, shoulder blades and other bones of a person, which creates the sound of teeth rubbing against bone. Hearing these sounds, people were immediately alarmed.

This fear of dangerous sounds has been passed down from generation to generation and has survived to this day. Therefore, even if you do not need to hunt to survive right now, you will still experience an instinctive disgust when hearing such sounds. Scientists have found that the sound of clattering nails on a blackboard has exactly the same frequency as that sound from the past, so hearing it is like hearing wild animals eating people.

To find out which area of ​​the brain is responsible for this response, Sukhbinder Kumar, a neurologist at Newcastle University School of Medicine in the UK, recruited 13 healthy volunteers and used functional magnetic resonance imaging (fMRI) to study which part of the human brain is responding. for the perception of this sound. It was found that when participants heard this sound, there was an interaction between the auditory cortex, which processes the sound, and the amygdala, which controls negative emotions, and the stronger the sound, the more active the amygdala.

The sound of nails scraping across the board passed through the cochlea and was transmitted to the brain, stimulating the amygdala. As soon as he exceeded the lower limit that the amygdala can withstand, it began to irritate. It then transmitted negative emotions such as disgust and fear directly into the auditory cortex. In simple terms, sound in the 2000-5000 Hz frequency range caused severe discomfort. Hearing this sound is like putting a fast-paced glass ball in your ear.

Back in 1986, three scientists from Northwestern University in the United States conducted a similar experiment. Under normal conditions, the frequency of sound waves that humans can hear is between 20 Hz and 20,000 Hz.

The researchers divided the sound into three parts – low, medium and high – and found that when the high-frequency sound was removed from the recording, the subjects still developed disgust. But if you filter out the mid-frequency sound, that is, remove the frequencies in the 2000-4000 Hz range, the participants in the experiment will no longer feel such dislike, and sometimes they may even find these sounds somewhat pleasant to the ear.

In other words, the frequency of annoying sounds to a person is in the range of 2000-4000 Hz. This conclusion is consistent with the results of the Kumar experiment. And the frequency of the sound of nails scratching a chalkboard is just in that range. Therefore, when you hear a sound like this, your body naturally begins to resist and you experience negative emotions.

If you really hate such sounds, start brainwashing yourself from now on. Convince yourself that these are great sounds, beautiful music, great melody. And maybe the next time the sound of nails scraping on a chalkboard won’t cut your ears so much.


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