1. What kind of sound is noise?
In the Law of People's Republic of China (PRC) on the Prevention and Control of Environmental Noise Pollution formulated by China, the phenomenon that it exceeds the national environmental noise emission standard and interferes with others' normal life, work and study is called environmental noise pollution. The decibel of sound is the unit of sound pressure level, which is recorded as dB. Used to indicate the size of the sound. The "People's Republic of China (PRC) Urban Regional Noise Standard" clearly stipulates the maximum limits of environmental noise in five urban areas:
Sanatorium area, senior villa area and senior hotel area, 50dB during the day and 40dB at night; Areas dominated by houses and cultural and educational institutions, 55dB during the day and 45dB at night; Residential, commercial and industrial mixed zone, 60dB during the day and 50dB at night; Industrial zone, 65dB during the day and 55dB at night; Urban trunk roads, inland waterways and areas on both sides of primary and secondary railways are 70dB during the day and 55dB at night (from 22: 00 to 6: 00am the next day at night).
According to national standards, the noise in residential areas should not exceed 50 decibels during the day and should be lower than 45 decibels at night. If it exceeds this standard, it will be harmful to human body. So, what is the noise standard of indoor environment? The fourth paragraph of Article 5 of the National Method for Measuring Environmental Noise in Urban Areas stipulates that when measuring noise indoors, the indoor noise limit is lower than the standard value of the area where it is located, that is, 10dB.
Two. Noise pollution is harmful to human physical and mental health.
Noise is a kind of environmental pollution, which is considered to be the third public hazard after air pollution and water pollution. Noise, like poisonous fog, pervades people, especially in cities and industrial areas. This is a deadly chronic toxin. As early as the seventh century BC, people knew that noise made people feel uncomfortable, and gradually people also knew that strong noise would harm people's health and even lead to death.
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.
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.
3. The cardiovascular system is damaged. 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%.
4. Noise can also cause nervous system dysfunction, mental disorders, endocrine disorders, 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.
5. 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.
6. Damage to women's 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.
7. 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%.
8. Noise damage 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 dB, 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%. Therefore, drivers should avoid the noise interference of stereo, otherwise it will easily cause traffic accidents.
9. Influence on people's psychology. When the noise exceeds 90 decibels, people's hearing will be damaged; When the noise exceeds 70 decibels, people cannot work normally; When the noise exceeds 50 decibels, it is difficult for people to fall asleep.
10. Influence of digestive system. Noise acts on the central nervous system, which will also cause changes in the secretion and peristalsis of the gastrointestinal system, change the metabolic process, cause metabolic disorders of vitamins, carbohydrates, fats, protein and inorganic salts, and lead to decreased gastric juice secretion, slow peristalsis and loss of appetite.
Health, nausea and vomiting and other symptoms.
Three. The main source of indoor noise
1. Traffic noise. The increasingly developed urban transportation industry has brought convenience and comfort to people's work and life, and also promoted economic development. However, with the increase of urban and rural vehicles and the increase of highway and railway traffic trunk lines, the noise of locomotives and motor vehicles has become the chief culprit of traffic noise, accounting for 75% of urban noise. According to statistics, Beijing is a world-famous noise pollution city. Although the number of urban vehicles is less than one tenth of that of Japan, the noise level is 1 times higher than that of Japan. In particular, some buildings facing the street suffered heavy losses.
2. Industrial machinery noise. This is also the main source of indoor noise pollution. Due to the impact, friction, jet and vibration generated by various power machines and working machines, sounds above 70 to 80 decibels can be generated. The noise in textile workshop, forging workshop, crushing workshop, steel plant, cement plant, air pump room and water pump room is quite serious. Although they have done some noise reduction, they still can't fundamentally eliminate the noise generated by the machine itself.
3. Urban building noise. Especially in recent years, the rapid development of urban construction, road construction, infrastructure construction, urban building development, old city reconstruction and indoor decoration of people's homes have all caused urban building noise. The noise of the construction site is generally above 90 decibels, and the highest is 130 decibels.
4. Noise in social life and public places. Such as commercial noise in public places, restaurants, buses, passenger trains, crowds, speakers, etc. According to statistics, the noise of social life and public places accounts for 14.4% of urban noise.
5. Household appliances directly cause indoor noise pollution. With the development of modernization of people's lives, the noise of household appliances is more and more harmful to people. According to the test, the noise generated by TV sets and tape recorders at home can reach 60 to 80 decibels, while that of washing machines is 42 to 70 decibels and that of refrigerators is 34 to 50 decibels. In recent years, family karaoke machines are widely used, and some people only care about their own enjoyment and ignore the happiness of others, which invisibly increases the intensity of noise pollution.
Four. Basic principles of noise control
Noise pollution is mainly caused by three factors, namely sound source, medium and receiver. Only when these three factors exist at the same time can they interfere with the listener. From these three aspects, noise can be controlled by reducing sound sources, limiting the spread of noise and blocking the reception of noise. In the specific noise control technology, three measures can be taken: sound absorption, sound insulation and noise elimination.
First, sound absorption
When sound waves are incident on the surface of an object, part of the sound energy will be absorbed by the object and converted into other forms of energy, which is called sound absorption. The sound absorption performance of materials is expressed by sound absorption coefficient, and the greater the sound absorption coefficient, the better the sound absorption performance of materials. The sound absorption performance of materials is related to the properties and structure of materials, the incident angle of sound waves and the frequency of sound waves. The sound absorption mechanism of porous sound absorption material is that there are countless tiny interconnected holes in the material. When sound waves are incident on the surface of these materials and then enter these tiny holes, the air in the holes will move, and the air near the hole wall and the fiber surface will not move easily due to friction and viscous motion resistance, so that acoustic energy will be converted into heat energy and consumed. Therefore, sound-absorbing materials with good performance should be porous, and the holes should be communicated with the outside world, so that sound waves can enter the material. If corresponding to 1000 Hz sound wave, the sound absorption coefficient of 10cm thick superfine glass wool is 0.87.
Second, sound insulation.
The method of sound insulation is to close the noise source and control the noise in a small space. This soundproof structure is called a soundproof cover. When the sound wave meets the shield, due to the change of the characteristic impedance of the interface, part of the incident sound energy is reflected, part of it is absorbed, and part of it continues to propagate through the shield. The sound insulation performance of materials can be expressed by sound transmission coefficient. The smaller the sound transmission coefficient, the less the sound energy penetration, and the better the sound insulation performance of the material. The sound insulation performance of materials is related to the structure and performance of sound insulation body and the frequency of incident sound waves.
Third, eliminate noise.
Noise elimination is to fix porous sound-absorbing materials in the inner wall or pipeline of the air flow channel in a certain way, so as to achieve the purpose of weakening aerodynamic noise, and the noise elimination amount can generally reach 10-50 dB.
Supplementary explanation of verb (abbreviation of verb)
The impact and harm of noise on people are directly related to the intensity of noise. In buildings, the measures to reduce noise are mainly sound insulation and sound absorption. Sound insulation is to isolate the sound source and prevent the noise generated by the sound source from spreading indoors. Planting trees on both sides of the road can insulate the houses on both sides. The sandwich structure made of porous materials and dense materials will also have good sound insulation effect. In order to eliminate noise, commonly used sound-absorbing materials are mainly porous sound-absorbing materials, such as glass wool, mineral wool, expanded perlite, perforated sound-absorbing board and so on. The sound absorption performance of materials depends on its roughness, flexibility, porosity and other factors. In addition, lawns and trees around buildings are also good sound-absorbing materials, so we plant flowers and trees, which not only beautify our living and learning environment, but also prevent noise from polluting the environment.
According to the World Health Organization, noise pollution will not only affect people's hearing, but also lead to mental syndromes such as hypertension, heart disease, memory loss and inattention. Research shows that the maximum acceptable volume of human hearing is 30 decibels. When indoor noise pollution exceeds 30 decibels, people's normal sleep will be disturbed, while living in a noise environment above 70 decibels will affect people's hearing and health.
Noise is a kind of environmental pollution, which is considered to be the third public hazard after air pollution and water pollution. Noise, like poisonous fog, pervades people, especially in cities and industrial areas. This is a deadly chronic toxin. As early as the seventh century BC, people knew that noise made people feel uncomfortable, and gradually people also knew that strong noise would harm people's health and even lead to death.