Is noise harmful after all?

Harm of noise to people

With the development of industrial production, transportation, urban architecture, and the increase of population density, the number of home facilities (audio, air conditioning, television, etc.). ) increase, environmental noise is becoming more and more serious, which has become a major public hazard that pollutes the human social environment. Noise is local, temporal and frequency. Noise will not only affect hearing, but also have adverse effects on people's cardiovascular system, nervous system and endocrine system, so some people call noise "a chronic poison that kills people." The physical and psychological damage caused by noise mainly includes the following aspects:

(A) interfere with rest and sleep, affecting work efficiency

(1) Interfere with rest and sleep. Rest and sleep are the necessary conditions for people to eliminate fatigue, restore physical strength and keep healthy. But the noise makes people fidget, making it difficult to rest and fall asleep. When people can't sleep after tossing and turning, they will feel nervous, shortness of breath, increased pulse, excited brain, and feel tired or weak limbs the next day. Thus affecting work and study, over time will get neurasthenia, manifested as insomnia, tinnitus, fatigue. After people fall asleep, even the noise of 40-50 decibels will change from a sleep state to a semi-sleep state. When people sleep, their brain activities are slow and regular, and they can get enough rest. However, in the semi-sleep state, the brain is still in a tense and active stage, which will make people unable to get adequate rest and physical recovery.

(2) reduce work efficiency. The study found that noise exceeding 85 decibels can make people feel agitated, and people will feel noisy and unable to concentrate on their work, resulting in reduced work efficiency.

(two) damage to the hearing and visual organs

We all have the experience that when we get off the plane or come out of the forging workshop, our ears are always buzzing, and we can't even hear each other's voice clearly, and we will recover after a while. This phenomenon is called auditory fatigue, which is a protective response of human auditory organs to the external environment. If people are affected by strong noise for a long time, their hearing will be weakened, leading to organic damage of hearing organs and hearing loss.

① Strong noise can cause ear discomfort, such as tinnitus, earache and hearing loss. According to the measurement, noise exceeding 1 15 decibels can also cause deafness. According to clinical medical statistics, if you live in a noise environment above 80 decibels, the number of deaf people can reach 50%. Medical experts believe that family noise is one of the reasons for children's deafness. Noise is more harmful to children's physical and mental health. Because children are immature, tissues and organs are delicate and fragile. Whether it is a fetus or a newborn child in the body, noise will damage the hearing organs, leading to hearing loss or loss. According to statistics, there are more than 70 million deaf people in the world today, and a considerable part of them are caused by noise. Expert research has proved that indoor noise is the main cause of children's deafness. If you live in noise above 85 decibels, the deaf can reach 5%.

(3) the damage of noise to vision. People only know that noise affects hearing, in fact, noise also affects vision. Experiments show that when the noise intensity reaches 90 decibels, the sensitivity of human visual cells decreases and the reaction time to identify weak light is prolonged. When the noise reaches 95 decibels, 40% people have dilated pupils and blurred vision; When the noise reaches 1 15 shellfish, the adaptation of most people's eyeballs to light brightness is weakened to varying degrees. Therefore, people who are exposed to noise for a long time are prone to eye fatigue, eye pain, dizziness and tears. At the same time, noise can also make color vision and visual field abnormal. It is found that noise reduces the visual field of red, blue and white by 80%.

(3) Physiological effects on human body

Noise is a malignant stimulus, which acts on the central nervous system for a long time. It can make the excitement and inhibition of the cerebral cortex unbalanced, and the conditioned reflex is abnormal, resulting in dizziness, headache, tinnitus, dreaminess, insomnia, palpitation, memory loss, inattention and other symptoms. In severe cases, it will lead to insanity. This kind of symptoms, the curative effect of drug treatment is very poor, but when out of the noise environment, the symptoms will be significantly improved. Noise can cause dysfunction of autonomic nervous system, which is manifested as increase or decrease of blood pressure, change of heart rate and aggravation of heart disease. Noise will reduce the secretion of saliva and gastric juice, reduce gastric acid, weaken gastric peristalsis, lose appetite and cause gastric ulcer. Noise will also have an impact on human endocrine function, such as: leading to female sexual dysfunction, menstrual disorder, increased abortion rate and so on. Noise also has a negative impact on children's intellectual development. According to the survey, children living in 75 decibel noise environment before the age of 3 will suffer different degrees of damage to their heart and brain function development. Children living in a noisy environment are 20% less intelligent than children living in a quiet environment. The psychological impact of noise on people is mainly to make people anxious, excited, fidgety and even lose their minds. In addition, noise is harmful to animals and buildings, and plants under noise do not grow well, and some even die.

① Damage to cardiovascular system. Noise is a risk factor for cardiovascular diseases, which will accelerate heart aging and increase the incidence of myocardial infarction. Medical experts have proved through human and animal experiments that long-term exposure to noise will increase adrenal secretion in the body, thus raising blood pressure. People who live in noise with an average of 70 decibels for a long time can increase the incidence of myocardial infarction by about 30%, especially at night. The survey found that the myocardial infarction rate of residents living beside the expressway increased by about 30%. 110/textile female workers were investigated. The incidence of hypertension was 7.2%, of which the contact intensity reached 100 dB noise, and the incidence of hypertension reached 15.2%.

② Damage to female physiological function. Women are threatened by noise, and there will be irregular menstruation, miscarriage, premature delivery, etc., such as causing female sexual dysfunction, menstrual disorder, and increased abortion rate. Experts conducted a three-year systematic investigation in seven regions, including Harbin, Beijing and Changchun, and found that noise can not only make female workers suffer from noise deafness, but also have a negative impact on their menstruation and fertility. In addition, it can also lead to miscarriage, premature delivery and even teratogenesis. Foreign countries have made a survey on the common situation of miscarriage and premature delivery of pregnant women in a certain area, and found that they live near an airport, and the culprit is the huge noise generated when the plane flies and lands.

③ Noise can also cause nervous system dysfunction, mental disorder, endocrine disorder, and even increase the accident rate. Noisy working environment can lead to dizziness, headache, insomnia, dreaminess, general fatigue, memory loss, fear, irritability, inferiority and even insanity. In Japan, there have been cases in which someone went insane because he couldn't stand the stimulation of train noise and finally committed suicide.

Utilization of noise

People have always hated noise. However, with the development of modern science and technology, people can also use noise to benefit mankind.

(1) Use noise to weed.

Scientists have found that different plants are not sensitive to different noises. According to this truth, people made a noise lawn mower. The noise generated by this noise herbicide can make the seeds of weeds germinate ahead of time, so that weeds can be removed with drugs before crop growth, and the smooth growth of crops can be ensured through the clever strategy of "playing hard to get".

(2) Using noise to generate electricity

Noise is a kind of energy pollution. For example, the sound power of a jet plane with a noise of 160 dB is about10000 W; ; The sound power of a large blower with a noise of 140 dB is about 100 W ... "Gathering sand into a tower" naturally attracts the interest of new energy developers. Scientists have found that artificial lithium niobate has the special function of converting acoustic energy into electrical energy at high frequency and high temperature. Scientists also found that when sound waves meet obstacles, acoustic energy will be converted into electrical energy. According to this principle, British scholars have designed and manufactured a tympanic membrane acoustic wave receiver, which is connected with a buzzer that can increase acoustic energy and concentrate energy. When the sound energy from the buzzer acts on the acoustoelectric converter, it can generate electricity. Using environmental noise to generate electricity seems to be just around the corner.

(3) using noise for refrigeration

As we all know, refrigerators can be refrigerated, but it is encouraging that a new refrigeration technology is being developed internationally, that is, a new technology using weak acoustic vibration for refrigeration. The first prototype has been successfully trial-produced in the United States. In an unusually simple cylinder with a diameter less than 1 m, several glass fiber plates with heat transfer function are stacked, and the cylinder is filled with helium or other gases. One end of the cylinder is sealed, and the other end is sealed with an elastic diaphragm. The wires on the diaphragm are connected with the magnetic voice coil to form a microphone. Sound waves act on the diaphragm, causing back and forth vibration, thus changing the pressure of gas in the cylinder. Because gas becomes hot when compressed and cold when expanded, refrigeration begins. It is not difficult to imagine that if these factors can be taken into account in buildings such as houses and factories in the future, the invisible scourge of noise can be overcome in one fell swoop, and buildings such as houses and factories can cool down and cool off the heat.

(4) using noise to remove dust

American researchers have developed a dust alarm with a power of 2 kW, which can emit noise with a frequency of 2000 Hz and a sound intensity of 160 dB. The device can be used for chimney dust removal and control dust particles and air pollution in high temperature, high pressure and high corrosion environment.

(5) Use noise to defeat the enemy.

Noise can also be used to subdue stubborn enemies. At present, a "noise bomb" has been developed, which can release a large number of noise waves between explosions, paralyze people's central nervous system and make people temporarily unconscious. This kind of bomb can be used against terrorists, especially hijackers.

(6) Using noise to diagnose diseases

As we all know, beautiful and melodious music can cure diseases. But how can noise be used for diagnosis? Recently, scientists have made a laser hearing diagnosis device, which consists of a light source, a noise generator and a computer tester. When in use, the micro-noise generator first produces weak and short noise to vibrate the eardrum, and then the microcomputer will display the data of the eardrum function according to the echo for the doctor to diagnose. It has the advantages of fast detection speed, no damage to eardrum and no pain, and is especially suitable for children. In addition, noise thermometry can also be used to detect human lesions.

(7) Active noise elimination.

Three commonly used noise reduction measures, namely noise reduction at sound source, noise reduction during propagation and noise reduction at human ear, are all passive. In order to actively eliminate noise, people invented the "active noise elimination" technology. Its principle is that all sounds are composed of a certain frequency spectrum. If a sound can be found, its spectrum is exactly the same as the noise to be eliminated, but its phase is just opposite (phase difference 180), and this noise can be completely cancelled. The key is how to get the noise-eliminated sound. The practical method is to start with the noise source itself and try to reverse the phase of the original noise through electronic circuits. From this point of view, active noise elimination technology is actually "fighting poison with poison".