Things that people know: why do scratching and squeaking sounds hurt us?

A. Questioner: Why does it hurt us to hear a scratch on a board?

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Questioner: Why does it hurt us to hear a scratch on a board??

A jarring sound accompanies the childhood memories of people my age - Those who had the privilege of studying in classes where the teacher writes in chalk on a large green board.
The squeaking sound of A fingernail and sometimes the chalk itself on the board: an annoying shriek that even without the harmful chalk dust justifies The transition to today's whiteboards.ate why certain sounds would cause us to recoil As a pair of harmless bones? Like many interesting questions, science has no answer to this one either. Which guarantees plenty of theories.

First of all, it is necessary to examine whether something is innate in us from birth Causes reluctance or has culture taught us that such noises
Worse than just different voices and strange in the environment. It turns out that there are indeed squeaking and scratching sounds such as those produced by friction Polystyrene (or Styrofoam in its popular name) or the rustling of metal parts are described as unpleasant And even as real suffering even when they are played to subjects who are not aware of their origin. Objective measures of distress such as the heart rate and the electrical conductivity of the skin show that squeaking and scratching sounds, even at low volume, evoke a reaction similar to that of a mild electric shock or a sound of pain-inducing intensity to the ear. 

Researchers Halpern and Blake went one step further: after producing a particularly horrific sound from the friction of a rake against slate, they separated the sound wave into its components and played different frequency ranges to the subjects individually. It turned out that the noise lost its horror when the low frequencies were removed from it and remained horrible when the high frequencies were removed. An acoustic comparison revealed a similarity between the sounds
Suffering from the warning calls of monkeys, the researchers hypothesized that our flinching response to scratching sounds stems from "residues" of a response reflex left in us from our evolutionary ancestors. It is easy to blame our monkey brothers for various problems of the human race, but this time we will find someone who will protect our brothers in the trees. It turns out that, contrary to what can be predicted from Halpern and Blake's hypothesis, monkeys do not show a special aversion to scratching sounds. A reflex response to a warning call should be expressed in vigilance and attention and not recoil from the sound.

Researcher Trevor Cox (Trevor J. Cox)  Conducted extensive research to sort and rank the disturbing sounds. In order to get results from many subjects and from a variety of ages and cultures, Cox turned to the Internet. On the site he built, surfers were asked to listen to different sounds and rate the discomfort that arose in them (Examples of annoying noises are concentrated here). The surfers were exposed to a wide range of noises from drums and airplane mirrors to the noisy eating of a cat and the crying of a baby. It turns out that the scratching sound of a fingernail on a chalkboard found itself in the center of the table: less horrible than the sound of a violin, the ringing of a cell phone or a loud argument from a soap opera and at the same level of discomfort as the angry barking of a dog. But, when the sound was accompanied by an image on the screen of a hand on a board, the sound became horrible to hear. Another sound that was tolerable as long as it was not accompanied by a picture is the sound of the drill used by a dentist, only when the picture of the doctor appeared did the sound become a serious nuisance. It seems that there are sounds that we have learned to hate because they are associated with unpleasant situations or because that is how the culture sees them. This relationship between noise nuisance and the visibility of the noise source has important implications for urban planning. It was found, for example, that vegetation hiding roads reduces the discomfort caused by traffic noise, even though acoustic measurements indicate that the sound reduction contributed by a hedge or a row of trees is marginal. Separating the road through landscaping reduces the subjective noise by about 10 decibels - more than a concrete wall that hides the road with the same efficiency. A study that examined the effect of noise on people living near a busy road found that a window overlooking a green garden significantly reduced the discomfort. And yet some results in Cox's research suggest that not everything is learned and there are sounds that we are innately afraid of. Squealing sounds (squealing of metallic objects rubbing against each other), sawing and of course microphone feedback caused a general reluctance regardless of the image on the screen or the location of the surfer on the globe. As expected from a reflex response, the magnitude of the horribleness of the shrill sounds depended on age: peaking at about age 20 and falling sharply above age 35, women showed greater discomfort than men when hearing these sounds. Some researchers believe that the aversion to squeaks and scratches is indeed inherent in us, but it is not an inheritance from our ape ancestors but an original human phenomenon. As Pythagoras discovered, humans have the ability to distinguish harmonic sounds. Language and music: two phenomena that distinguish us from the monkeys sharpen our abilities to receive harmonic sounds, that is, those made up of frequencies whose ratio is that of whole and small numbers. An octave, for example, is an interval between two notes, the frequency of one of which is twice the frequency of the other. The sounds of the human voice are almost always accompanied by their harmonies. A sound with a frequency of 220 Hz (that is, one in which the pressure wave will hit the ear 220 times per second) will naturally be accompanied by sounds of 440, 660, 880 Hz, etc. The evolution that developed in us the ability to produce speech and singing sounds (the most ancient form of music) and the ability to decipher these sounds also brought the ability to differentiate between the harmonious voices and the "noise" which is a combination of sounds that have no harmony (dissonance).  Mother's lullaby In our infancy our brains learned to filter the harmonic voices from the noise and the evolution we have gone through since we created language has developed this vital ability in us. A squeak or scratch forces the brain to look for a harmony that doesn't exist in the jumble of sounds that vibrate the eardrum and it really doesn't like it.

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