Try to explain it sosedyam
It is no secret that the squeaking chalk on the blackboard or fingernails scratching any rough surface, you can make some people sёzhitsya disgust - for them this quiet sound is like torture. According to researchers curious phenomenon, blame - especially the perception of sound generated in the course of development of the species Homo sapiens.
Analyzing the results of a study conducted in 2011, the year, scientists have suggested that due to the specific shape of the ear the sound of a particular frequency range seem human louder than others. According to experts, the ears of people in the overall sound picture emit audio signals in the course of evolution have become vital - for example, very few people from the adults leave indifferent sounds of crying of infants, because the fast response of our ancestors to the cry baby increases the safety of the offspring and as a consequence - improves survival of the species. Let today fathers and mothers do not have to run headlong to the cries of the children of to pry him from the jaws of a saber-toothed tiger, piercing cry of the child (even a stranger) creates in the soul a desire to eliminate its cause.
Frequencies through which the sound becomes unbearable, refer to the range of 2000 - 4000 Hz are present in fingernails scratching on a tree, gnashing metal sponge for dishes, squeak foam noise elektropily- almost all the sounds that could cause a human aversion. Interestingly, after the removal of these frequencies a person ceases to perceive a sound as bad, although clean audio signals from other tonal components of noise and virtually no effect with regard to them.
Further experiments showed that the "goose bumps on the skin," arising from the hideous sounds - not that other, as a side effect of the body's physiological response to the strongest audio stimulus. When a person hears the squeak of chalk on the blackboard, he observed all the signs of stress - for example, changing blood pressure, heart rate, and the electrical conductivity of the skin.
By the way, before the staff of the University of Newcastle (UK) ranked the most annoying sounds that are sure you are familiar with. To change the electrical conductivity of your skin, just remember them:
Rattle knife bottle Scratching fork glass creaking chalk on a blackboard line friction on the bottle gnashing nails on wood Female scream squeal circular saw or other power tools creaking bicycle brakes Child crying sound of an electric drill