A strange thing happened in the United States: trees on both sides of the highway died for no reason. At first, people thought that trees were poisoned by car exhaust. Later, after repeated investigation and research, it became clear that the culprit was the vibration caused by passing cars, which destroyed the contact between tree roots and soil and eventually led to the death of trees. Vibration can do so much harm to plants. What about human beings
the world in which human beings live is simply a vibrating world. The subway in the city is vibrating. People have to be swayed by buses on their way to work. 1n factories, machine tools such as turning, grinding, planing, milling and drilling all produce different frequencies of vibration. Vibration can seriously harm human health, so it is listed as a major pollution of modern industry. Scientists have found that many serious diseases are caused by vibration
studies have shown that people have different responses to different frequencies of vibration. Some people have done human experiments, let the subject sit in a chair, give him a vibration of low intensity, the vibration frequency changes slowly from low to high. The results showed that when the vibration frequency was lower than 1 Hz, the main feeling was vibration in the head. After several minutes, there were uncomfortable feelings such as muscle pain; When the vibration frequency is 1-2 Hz, people will doze off for a long time; When the frequency is 3-4 Hz, there is a greater sense of vibration in the waist and chest; When the frequency is 5-8 Hz, the feeling of discomfort and discomfort reaches the maximum, and the breathing and speech are interfered; At 8 Hz, the waist vibrates; At 9-30 Hz, the face, cheek and neck vibrated and the vision was disturbed; When the vibration frequency exceeds 30 Hz, the above-mentioned feeling becomes weaker
Why do people feel different when the vibration frequency changes? 1t turns out that the human body itself has many vibration “devices”. When the vibration frequency of the object is the same as that of the human body, the vibration response of the human body reaches the maximum, that is, resonance occurs. According to the measurement, the maximum frequency of human body reaction is 5-8 Hz, followed by 10-12 Hz, which is mainly caused by thoracolumbar visceral resonance; Again, 20-25 Hz. Different organs of the human body also have different responses to vibration. For example, the hand is most sensitive to 18-50 Hz vibration, the head is 2-30 Hz and 500-1000 Hz, the nervous system is 250 Hz, and the upper and lower jaw is 6-8 Hz. This is why the visual interference is the most serious when the vibration frequency is 18-50 Hz, the hand operation is the most serious when the vibration frequency is 30-40 Hz, and the language barrier appears when the vibration frequency is 6-8 Hz
how much vibration can people bear? Generally speaking, when the acceleration amplitude of vibration below 20 Hz reaches 0.01g (1g is equivalent to 1 times of gravity), people begin to pay attention to it; 0.05g above will make people feel comfortable; After more than 0.3g, it will cause imbalance of human organs, start to feel dizzy, heavy headed, sleepy, tired, attention decline and so on. Organ dysfunction has serious consequences, but also lead to nervous system, cardiovascular system and motor system disorders
the most important way to prevent vibration hazards is to try to reduce mechanical vibration, or use vibration isolation, vibration reduction and other devices. 1f people work in vibration environment, they can use elastic cushion or strap to fix the body to reduce the impact of vibration. Of course, it’s better not to go to places with serious vibration pollution
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