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Noise zàoshēng
That is, noise. It is a class of sound that causes annoyance, or excessive volume that is harmful to human health.
Noise usually refers to those unpleasant, annoying sounds. The waveform of noise is disorganized.
From the point of view of environmental protection, any sound that affects people's normal study, work and rest, or any people in some occasions "do not need the sound", are all belong to the noise.
Noise pollution mainly comes from transportation, vehicle horns, industrial noise, construction, social noise such as concert halls, loudspeakers, morning market and people talking loudly.
Our country formulated the "Chinese People's *** and State Environmental Noise Pollution Prevention and Control Law" in the more than the nationally specified environmental noise emission standards, and interfere with other people's normal life, work and study of the phenomenon known as environmental noise pollution. The decibel of sound is the unit of sound pressure level, recorded as dB, which is used to indicate the size of the sound. People's Republic of China *** and the State Urban Area Noise Standards" in the city clearly stipulates the five categories of areas of the maximum limit of environmental noise:
Convalescent area, senior villa area, senior hotel area, daytime 50dB, 40dB at night; to residential, cultural and educational institutions mainly in the area, daytime 55dB, 45dB at night; residential, commercial, industrial mixed areas, daytime 60dB, nighttime 50dB; industrial areas, daytime 60dB, nighttime 50dB; industrial areas, industrial areas, daytime 60dB, nighttime 50dB, nighttime 50dB. 50dB; industrial areas, 65dB during the day, 55dB at night; road traffic in the city on both sides of the main roads, inland waterways, railroads, major and minor trunk lines, 70dB during the day, 55dB at night, (night refers to 22:00 to 6:00 the next morning).
According to national standards, the noise in residential areas, the daytime can not exceed 50dB, the night should be less than 45dB, if more than this standard, it will be harmful to the human body. So, what is the noise standard in the indoor environment? National "Measurement Methods of Environmental Noise in Urban Areas" in Article 5, paragraph 4, the noise measurement indoors, the indoor noise limit is lower than the standard value of the region 10dB.
Sources of Urban Environmental Noise
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Modern cities in the ambient noise there are four main sources of noise:
①Traffic Noise: the main references are Motor vehicles, airplanes, trains and ships and other means of transportation in operation issued by the noise. The noise source of these noises is mobile, and the scope of interference is large.
② industrial noise: mainly refers to the noise generated by industrial production and labor. Mainly from machines and high-speed running equipment.
③ Construction noise: mainly refers to the noise generated by the construction site. In the construction to use a large number of various power machinery, to excavate, holes, mixing, and frequent transportation of materials and components, thus generating a lot of noise.
④Social life noise: mainly refers to people in business transactions, sports competitions, parades and rallies, entertainment venues and other social activities in the noise, as well as recorders, televisions, washing machines and other home appliances cacophony, the noise is generally below 80 decibels. Such as washing machines, sewing machines, noise for 50 - 80 decibels, the noise of electric fans for 30 to 65 decibels, air-conditioners, televisions for 70 decibels.
Noise control basic way
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In order to prevent noise, China's famous acoustician Professor Ma Dayou has summarized and studied the existing domestic and foreign various types of noise hazards and standards, put forward three recommendations:
① In order to protect people's hearing and health, the allowable value of the noise in the 75 ~ 90 dB.
①To protect people's hearing and physical health, the permissible noise level is 75~90 dB. ②To protect conversation and communication, the permissible environmental noise level is 45~60 dB.
③ For sleeping time, it is recommended to be 35~50 dB.
Our psychological community believes that the control of noise environment, in addition to considering the human factor, must also take into account the economic and technical feasibility. Adequate noise control must take into account the entire system consisting of the noise source, the path of transmission, and the recipient. Measures to control noise can be directed at all or any of these three components. Noise control includes:
① Control of noise sources. Reduce the noise of the source, industry, transportation can choose low-noise production equipment and improve the production process, or change the movement of the noise source (such as damping, vibration isolation and other measures to reduce the vibration of the solid sound-emitting body).
② Blocking noise propagation. Reduce noise in the transmission pathway, control the propagation of noise, change the sound source has been issued by the noise transmission pathway, such as the use of sound absorption, sound insulation, sound barriers, vibration isolation and other measures, as well as rational planning of urban and architectural layout and so on.
③ attenuate noise at the human ear. Noise protection of the recipient or the recipient organ, in the sound source and transmission pathway can not take measures, or take acoustic measures still can not achieve the desired effect, it is necessary to take protective measures for the recipient or the recipient organ, such as long-term occupational noise exposure workers can wear ear plugs, ear muffs or helmets and other ear protectors.
Although noise control is now technically mature, but because of modern industry, transportation industry is very large, to take the noise control of the number of enterprises and places, so in the prevention of noise problems, must be from the technical, economic and effect of comprehensive trade-offs. Of course, specific issues should be specifically analyzed. In the control room, design room, workshop or long-term work of the staff, the intensity of the noise should be low; warehouse or less people to go to the workshop or open space, the noise is slightly higher can be. In short, the treatment of different times, different places, different nature and different duration of the noise, there should be some difference.
Noise harm to people
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With the development of industrial production, transportation, urban construction, as well as the increase in population density, the increase in the number of home facilities (stereo, air conditioning, television, etc.), the environmental noise is becoming increasingly serious, and it has become a major public nuisance to pollute the environment of human society. Noise is localized, temporary and multiple. Noise not only affects hearing, but also adversely affects the cardiovascular system, nervous system, endocrine system, so some people call noise "a chronic poison that kills". Noise brings physiological and psychological harm to people mainly in the following aspects:
(a) Interference with rest and sleep, affecting work efficiency
① Interference with rest and sleep. Rest and sleep are necessary for people to eliminate fatigue, restore physical strength and maintain health. But the noise makes it difficult for people to rest and sleep. When people toss and turn and can't sleep, they will be nervous, shortness of breath, pulse rate increases, the brain is more than just excitement, the next day will feel tired, or limb weakness. Thus affecting the work and study, over time, will get neurasthenia, manifested as insomnia, tinnitus, fatigue. After a person enters sleep, even 40-50 decibels of lighter noise interference, but also from the sleeping state into a semi-sleeping state. People in the sleeping state, brain activity is slow and regular, can get enough rest; and semi-sleeping state, the brain is still in a tense, active stage, which will make people do not get enough rest and physical recovery.
② make work less efficient. Research has found that noise exceeding 85 decibels will make people feel distracted, people will feel noisy, and thus unable to concentrate on their work, and as a result, it will lead to lower work efficiency.
(B) damage to the auditory and visual organs
We all have such experience, from the airplane down or from the forging workshop out, the ears are always buzzing, even can not hear each other speak, after a while will recover. This phenomenon is called auditory fatigue, is the human auditory organ of the external environment of a protective response. If a person is subjected to strong noise for a long time, the hearing will be weakened, which will lead to organic damage to the auditory organs, resulting in hearing loss.
①Strong noise can cause ear discomfort, such as tinnitus, earache, hearing damage. It has been determined that more than 115 decibels of noise can cause deafness. According to clinical statistics, if you live in a noise environment of more than 80 decibels, the deafness can be up to 50%. Medical experts believe that household noise is one of the causes of childhood deafness. Noise is more harmful to children's physical and mental health. Because children's development is not yet mature, the tissues and organs are very delicate and fragile, whether it is the body of the fetus or just out of the child, noise can damage the hearing organs, so that hearing loss or loss. According to statistics, there are more than 70 million deaf people in the world today, a considerable part of which is caused by noise. Expert research has proved that indoor noise in the home is the main cause of deafness in children, if living in more than 85 decibels of noise, deafness can be up to 5%.
③ Noise damage to vision. People only know that noise affects hearing, in fact, noise also affects vision. Tests show that: when the noise intensity reaches 90 decibels, the sensitivity of human visual cells decreased, recognition of weak light reaction time is extended; noise reaches 95 decibels, 40% of the people's pupils dilated, fuzzy vision; and the noise reaches 115 bei, the majority of people's eyes on the brightness of the light of the adaptation has a varying degree of weakening. So long time in the noise environment is very easy to occur in the eye fatigue, eye pain, eye and visual tear and other eye damage phenomenon. At the same time, the noise will also make color vision, visual field abnormalities. Investigation found that the noise of red, blue, white color vision shrinkage of 80%.
(3) Physiological effects on the human body
Noise is a kind of malignant stimulus, long-term effect on the central nervous system, can make the cerebral cortex of excitation and inhibition dysregulation, conditioned reflex abnormalities, dizziness, headache, tinnitus, dreamy, insomnia. Panic, memory loss, inattention and other symptoms, serious cases can produce insanity. This symptom, drug treatment efficacy is very poor, but when out of the noise environment, the symptoms will be significantly better. Noise can cause dysfunction of the plant nervous system, manifested in increased or decreased blood pressure, heart rate changes, heart disease aggravation. Noise can reduce the secretion of saliva and gastric juice, lower gastric acid, weaken gastric peristalsis, loss of appetite, and cause gastric ulcers. Noise will also have an effect on human endocrine function, such as: lead to female sexual dysfunction, menstrual disorders, abortion rate increases. Noise on the intellectual development of children also has a negative impact, according to the survey, 3 years old children living in a 75 dB noise environment, their heart and brain function development will be damaged to varying degrees, children living in a noisy environment, the level of intellectual development than the quiet conditions under the children's 20% lower. The psychological impact of noise on people is mainly to make people worry, agitation, irritability, and even lose their minds. In addition, noise is also damaging to animals and buildings, and plants grow poorly under noise, and some even die.
① Damage to cardiovascular. Noise is a risk factor for cardiovascular disease, noise will accelerate heart aging, increase the incidence of myocardial infarction. Medical experts by human and animal experiments have proved that long-term exposure to noise can make the body adrenal secretion increase, so that blood pressure rises, in the average 70 decibels of noise in the long-term life of people, can make the incidence of myocardial infarction increased by 30% or so, especially at night noise will make the incidence higher. The survey found that the residents living next to the highway, myocardial infarction rate increased by about 30%. Investigation of 1,101 female textile workers, the incidence of hypertension was 7.2%, of which the intensity of exposure to 100 decibels of noise, the incidence of hypertension reached 15.2%.
② damage to female physiology. Women threatened by noise, there can be menstrual disorders, miscarriage and premature birth, such as leading to female sexual dysfunction, menstrual disorders, abortion rate increases. Experts have conducted a 3-year systematic survey in 7 regions, such as Harbin, Beijing and Changchun, and found that noise not only makes female workers suffer from noise deafness, but also has a negative impact on their menstruation and fertility. In addition, it can lead to miscarriage, preterm labor, and even teratogenicity. Foreign countries have a region of pregnant women commonly occurring miscarriage and preterm birth for the investigation, the results found that they live in an airport around, the culprit is that the huge noise generated by the landing of the aircraft.
③ Noise can also cause such as nervous system dysfunction, mental disorders, endocrine disorders and even higher accident rates. High noise work environment, can make people appear dizziness, headache, insomnia, dreams, general weakness, memory loss and fear, irritability, low self-esteem and even insanity. In Japan, there have been examples of people who could not stand the stimulation of train noise and became psychotic and eventually committed suicide.
Noise utilization
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Noise has always been detested by people. However, with the development of modern science and technology, people can also utilize noise for the benefit of mankind.
(1) the use of noise weed
Scientists found that different plants are not the same degree of sensitivity to different noise. According to this reasoning, people made a noise weeder. This noise weeder noise can make the seeds of weeds sprout in advance, so you can use drugs to get rid of weeds before the crop grows, with the "want to capture the secret" strategy to ensure the smooth growth of crops.
(2) the use of noise power generation
Noise is a kind of energy pollution, such as noise up to 160 dB of the jet aircraft, the sound power of about 10,000 W; noise up to 140 dB of the large-scale blower, the sound power of about 100 W. "Gathering sand can be made into a tower," which naturally aroused the interest of new energy developers. This has naturally aroused the interest of new energy developers. Scientists have discovered that artificial lithium niobate has a special function of converting acoustic energy into electrical energy at high frequencies and temperatures. Scientists also found that when sound waves encountered the barrier, acoustic energy will be converted into electrical energy, British scholars is based on this principle, designed and manufactured tympanic membrane acoustic receivers, receivers and the ability to increase sound energy, energy collection **** sounders connected, when the sound energy from the **** sounders to the acoustic-electrical converter, you can send out the electricity to. It seems that the use of environmental noise power generation is just around the corner.
(3) the use of noise to refrigeration
As we all know, refrigerators can be cooled, but it is encouraging that the world is currently developing a new refrigeration technology, that is, the use of weak acoustic vibration to refrigeration of the new technology, the first prototype has been in the United States successful trial production. In an unusually simple structure, less than 1 m in diameter in a cylinder stacked with a few pieces of glass fiber plate to play a role in heat transfer, the cylinder is filled with helium or other gases. One end of the cylinder sealed, the other end of the elastic diaphragm closed, a wire on the diaphragm and magnet-type voice coil connection to form a micro microphone, sound waves acting on the diaphragm, caused by the vibration back and forth, and then change the pressure of the gas inside the cylinder. As the gas becomes hot when compressed, expansion when cooled, so refrigeration began, it is not difficult to imagine, the future of housing, factories and other buildings such as can be taken into account these factors, you can subdue the noise of this invisible scourge in one fell swoop for the homes, factories and other buildings cool down the summer heat.
(4) the use of noise in addition to dust
U.S. researchers developed a power of 2 kW dust alarm, which can be issued at a frequency of 2,000 Hz, the sound strength of 160 dB of noise, this device can be used for chimney dust, control of high temperatures, high pressures, high corrosion of the environment in the dust particles and atmospheric pollution.
(5) the use of noise to defeat the enemy
The use of noise can also subdue the enemy, has developed a "noise bomb", can be released between the explosion of a large number of noise waves, paralyzing the central nervous system, so that people are temporarily comatose, the bomb can be used to deal with terrorists, especially hijackers and so on.
(6) the use of noise diagnosis
Wonderful, pleasant music can cure the disease, which has been known to everyone. But how can noise be used to diagnose diseases? Recently, scientists made a laser hearing diagnostic device, which consists of a light source, noise generator and computer tester three parts. When used, it first by the micro-noise generator to produce weak short noise, vibration of the eardrum, and then the micro-computer will be based on the echo, the eardrum function of the data displayed for the doctor to diagnose. It tests quickly, does not damage the eardrum, has no pain and is especially suitable for children. In addition, noise thermometry can be used to detect human lesions.
(7) Use of noise active noise elimination
The three noise reduction measures usually used, namely, noise reduction at the source, noise reduction in the propagation process and noise reduction at the human ear, are negative and passive. In order to proactively eliminate noise, people invented the "active anechoic" technology. Its principle is: all sounds are composed of a certain frequency spectrum, if you can find a sound, its spectrum and the noise to be eliminated exactly the same, only the phase is just the opposite (180 ° difference), the noise can be completely canceled out. The key lies in how to get that noise canceling sound. The actual approach is: from the source of the noise itself, trying to reverse the phase of the original noise through electronic circuits. In this way, the technique of active noise cancellation is actually "fighting fire with fire".
Noise in circuits
The term noise in electronic circuits can be generalized to mean all signals other than the destination signal. Initially, those electronic signals that cause the noise emitted by an audio device such as a radio were called noise. However, the consequences of some non-purpose electronic signals on electronic circuits are not always related to sound, and thus the concept of noise was gradually expanded. For example, the electronic signals that cause the visual screen to have the white class ah stripes are also known as noise. May be said, in addition to the purpose of the circuit of all signals, regardless of whether it affects the circuit, can be called noise. For example, ripples or self-excited oscillations in the supply voltage can adversely affect the circuit, causing the audio device to emit an alternating current sound or causing the circuit to operate incorrectly, but sometimes may not lead to these consequences. Such ripples or oscillations are
referred to as a type of noise in the circuit. There is also a certain frequency of the radio wave signal, the need to receive this signal to the receiver, it is the normal purpose of the signal, but to another receiver it is a non-purpose signal, that is, noise. In electronics often use the term interference, sometimes confused with the concept of noise, in fact, there is a difference. Noise is an electronic signal, and interference refers to a certain effect, is due to noise causes an adverse reaction to the circuit. Whereas there is noise in a circuit, there is not necessarily interference. In digital circuits. Often can be observed with an oscilloscope in the normal pulse signal mixed with some small spike pulse is not expected, but a noise. However, due to the circuit characteristics of the relationship, these small spikes in the pulse is not enough to make the logic of the digital circuit is affected by the chaos, so it can be considered that there is no interference.
When a noise voltage is large enough to disrupt a circuit, that noise voltage is called an interference voltage. And a circuit or a device, when it can also maintain normal operation when the maximum noise voltage added, called
for the circuit or device interference tolerance or immunity. In general, the noise is difficult to eliminate, but can try to reduce the intensity of the noise or improve the immunity of the circuit, so that the noise does not form interference.