When fingernails scratch the blackboard

  In life, there are many voices that can make people feel uncomfortable. For example, the sound of electric drills, bicycle brakes, and the sound of fingernails across the blackboard are even more maddening. Here comes the question: Why does the sound of fingernails scratching the blackboard make people feel scalp numbness and even trembling?
  As we all know, sound is sound waves produced by vibrations. The frequency of the sound wave determines the pitch, the higher the frequency, the higher the pitch, and the amplitude of the sound wave determines the volume of the sound. The sound that can be recognized by the human ear is called “audible sound”, and the frequency is between 20 Hz and 20,000 Hz. The basic frequency of the sound that people usually speak is between 80 Hz and 260 Hz. So, according to the change of sound frequency, is it true that the higher the frequency of the sound heard, the more uncomfortable people will be? In fact, the level of sound frequency and the degree of discomfort are far from being a matter of addition and subtraction.
  In order to find the reason, the researchers analyzed the high, middle and low frequencies of the sound of fingernails scratching the blackboard, and removed the high frequency part first, which made people feel uncomfortable when they heard it. Next, the researchers removed the middle and low frequency parts, and people felt much more comfortable when they heard it. In fact, the harsh sound that people hear is mainly related to frequency. Higher frequency sounds can make people feel harsh and feel very uncomfortable. To be exact, it is difficult for the human ear to accept the sound of 2000 Hz to 4000 Hz. Why does the sound between this frequency make people feel harsh and uncomfortable? This is mainly related to the human auditory system and brain.
  In the human brain, there is an area called the amygdala, which controls the human fear emotion. In the experiment, the researchers scanned the brains of the subjects while playing an unpleasant sound, and found that the amygdala activity of the subjects was abnormally obvious, and the more obvious the brain response, the more anxious and uncomfortable the subjects were, and the body also reacted naturally. There are a series of reactions, such as rapid heartbeat and high blood pressure. Of course, there is no doubt that the sound of fingernails on a blackboard has been found to be one of the most repulsive sounds of the human brain. Researchers believe that when hearing this sound in ancient times, people subconsciously believed that there was danger approaching, and this genetic gene has been preserved by humans, causing the brain to still have a sense of panic when hearing this sound. But I couldn’t find an outlet to release this panic, so I turned this panic into “scalp tingling”, even trembling.
  Interestingly, although the sound of nails across the blackboard is a very disgusting sound to the human brain, the researchers found in another study that if the subjects heard the sound of nails across the blackboard, telling the subjects it was For a part of the music, although the subjects still felt a sense of panic in their brains, the subjective disgust was significantly weakened. Therefore, when you hear the sound of fingernails scratching the blackboard, in addition to escaping and covering your ears, you can also try to say silently in your heart: this is music, this is music…