Noise is the sound produced when the generator is irregular. Sound is caused by the vibration of objects and propagates in a certain medium (such as solid, liquid and gas) in the form of waves. Noise pollution usually refers to man-made. From the physiological point of view, any sound that interferes with people's rest, study and work, that is, unnecessary sound, is collectively called noise. When noise has a bad influence on people and the surrounding environment, noise pollution is formed. Since the industrial revolution, the creation and use of various mechanical equipment has brought prosperity and progress to mankind, but at the same time, it has also produced more and more noise.
Noise pollution, water pollution, air pollution and solid waste pollution are called the four major environmental problems in the world.
Classification of noise
According to the mechanical characteristics of sound source, noise pollution can be divided into: noise caused by gas disturbance, noise caused by solid vibration, noise caused by liquid impact and electromagnetic noise caused by electromagnetic action.
Noise can be divided into:: 1000Hz high frequency noise.
Noise can be divided into steady noise, unsteady noise, fluctuation noise, intermittent noise and impulse noise according to its time-varying characteristics.
Noise is caused by natural phenomena (see natural noise) and man-made. Therefore, it is also divided into natural noise and man-made noise.
noise source
(1) Traffic noise: including noise generated by motor vehicles, ships, subways, trains and airplanes. Due to the sharp increase in the number of motor vehicles, traffic noise has become the main source of urban noise.
(2) Industrial noise: noise generated by various equipment in the factory. The sound level of industrial noise is generally high, which has a great impact on workers and surrounding residents.
(3) Construction noise: mainly from the noise generated by construction machinery. Construction noise is characterized by high intensity, which mostly occurs in densely populated areas, seriously affecting the rest and life of residents.
⑷ Social noise: It includes people's social activities and noise emitted by household appliances and audio equipment. Although the noise level of these devices is not high, they are closely related to people's daily life, which makes people fidget during rest, which is particularly annoying and easily leads to neighborhood disputes.
(5) Noise pollution in family life.
noise characteristic
The size of sound is related to "sound pressure"; The sharpness or heaviness of sound is related to the level of "audio"; Whether the sound is pleasant or noisy is related to whether the "tune" is harmonious.
(1) Audio Audio is the frequency of sound. The number of times a vibrating object vibrates per second is the vibration frequency of the object, and the unit of frequency is hertz. Generally speaking, waves with vibration frequency between 20 Hz and 20000 Hz can be heard by human beings, so they are called sound waves, and the vibration source of sound waves is called sound source. Below 20 Hz and above 20000 Hz belong to infrasound and ultrasonic respectively, which can't be heard by human ears.
(2) Sound pressure acoustic energy spreads out in the air because the vibrating object causes the local pressure change of the surrounding air through vibration, causing the local density change of the surrounding air, and the local density change causes the pressure change of the far air. In this way, pressure changes will be transmitted to further parts, which will lead to sound transmission. In the process of sound propagation, the pressure change of air pressure relative to atmospheric pressure is called sound pressure, and the unit is Pa. The field of human hearing is quite broad, with an average of about 2× 10-5-20 Pa. We can hear the volume of the strongest sound source, which may be 200,000 times that of the weakest sound source.
The expression unit is the overwhelming logarithmic expression of sound, that is, the sound pressure level is used to express the volume. The unit of sound pressure level is decibel. The sound pressure level of the sound we hear in our daily life is about 0- 140 dB. The intensity of noise is also expressed by sound pressure level. The lowest sound level that normal people can feel is 1 dB. Whispering softly is about 30 decibels. The conversation language separated by 1 m is about 60 decibels. It's about 80 decibels on the bus. The noise of heavy trucks, weaving workshops and subways is about 100 dB.
noise characteristic
Noise is not only a public hazard, but also has the characteristics of public hazard. At the same time, as a sound, it also has acoustic characteristics.
(1) noise pollution characteristics
Because noise belongs to sensory pollution, it is different from other harmful and toxic substances. First of all, it has no pollutants, that is, when noise spreads in the air, it will not leave any toxic substances to the surrounding environment; Secondly, the impact of noise on the environment is not cumulative and persistent, and the transmission distance is limited; The noise source is dispersed. Once the sound source stops sounding, the noise disappears. Therefore, noise can't be treated centrally and needs to be controlled by special methods.
(2) Acoustic characteristics of noise
Simply put, noise is sound, which has all the characteristics and laws of acoustics. However, the impact of noise on the environment is related to its intensity. The stronger the noise, the greater the impact. The physical quantity to measure the noise intensity is the noise level.
noise control
In order to reduce the impact of noise on the surrounding environment and human beings, the main noise control methods are to isolate or protect noise sources, noise propagation paths and receivers, and block or absorb noise energy. For example, the noise source (motor) is equipped with shock-proof spring or rubber to absorb vibration or cover the whole motor. The way of transmission is generally to use sound barriers to block the spread of noise. The protection of the receiver is generally sound insulation window, earplug, etc.
Governments all over the world usually have corresponding laws or regulations to control excessive noise.
Noise pollution is harmful to people, animals, instruments and buildings, and its degree of harm mainly depends on the frequency, intensity and exposure time of noise. Noise hazards mainly include:
Eight Harms of Noise Pollution
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. Cardiovascular system damage
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, short of breath, rapid pulse and excited brain, and they will 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 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.
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.
Control noise pollution
In order to prevent noise, Professor Ma, a famous Chinese vocalist, summarized and studied the hazards and standards of various noises at home and abroad, and put forward three suggestions:
(1) In order to protect people's hearing and health, the allowable value of noise is 75~90 decibels.
(2) Ensure conversation and communication, and the allowable value of environmental noise is 45~60 decibels. [ 1]
(3) It is recommended to sleep at 35~50 decibels.
In buildings, the measures to reduce noise mainly include
Sound insulation and 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.
Psychologists in China believe that the control of noise environment should not only consider human factors, but also consider economic and technical feasibility. Adequate noise control must consider the whole system composed of noise source, sound propagation mode and sound receiver. Noise control measures can be aimed at the above three parts or any of them. The contents of noise control include:
(1) To reduce the noise of sound source, industry and transportation can choose low-noise production equipment and improve production technology, or change the motion mode of noise source (such as damping and vibration isolation to reduce the vibration of solid sound generator).
(2) Reduce the noise in the sound propagation path, control the noise propagation, change the noise propagation path that has been emitted by the sound source, such as taking measures such as sound absorption, sound insulation, sound barrier and vibration isolation, and rationally plan the layout of cities and buildings.
(3) When the noise protection of the receiver or the receiver fails to take measures in terms of sound source and transmission route, or the acoustic measures still fail to achieve the expected effect, it is necessary to take protective measures for the receiver or the receiver. For example, workers who have been exposed to occupational noise for a long time can wear ear protectors such as earplugs, earmuffs or helmets.
Although noise control is technically mature now, many enterprises and places adopt noise control because of the large scale of modern industry and transportation. Therefore, in the aspect of noise prevention, we must make a comprehensive balance from the aspects of technology, economy and effect. Of course, specific problems should be analyzed in detail. In outdoor, design room, workshop or places where employees work for a long time, the noise intensity should be low; Warehouses or workshops with few people or open places are slightly noisy. In a word, the treatment of noise should be different at different time, place, nature and duration.
Several methods to prevent and control noise pollution
① The energy of sound in propagation decreases with the increase of distance, which can keep the noise source away from the place where it needs to be quiet and achieve the purpose of noise reduction. (2) The radiation of sound is generally directional. When the distance from the sound source is the same but the direction is different, the received sound intensity is also different. But when most sound sources radiate noise at low frequency, the directivity is very poor; With the increase of frequency, the directivity increases. Therefore, controlling the propagation direction of noise (including changing the emission direction of sound source) is an effective measure to reduce noise, especially high-frequency noise. ③ Establish a sound barrier, or use natural barriers (soil slopes and hills) and other sound insulation materials and structures to block the spread of noise. (4) Using sound-absorbing materials and sound-absorbing structures, the noise acoustic energy in transmission is converted into heat energy. ⑤ In urban construction, adopt reasonable urban noise prevention and control planning. In addition, vibration isolation measures are taken to reduce the noise propagation caused by solid vibration.
Utilization and application of noise
Although noise is one of the four major public hazards in the world, it is still useful:
Noise weeding scientists have found that different plants have different sensitivities to different noises. People make noise herbicides. 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".
As we all know, noise diagnosis and beautiful 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. Three noise reduction measures commonly used in active noise reduction, 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".
Noise can inhibit the growth rate of cancer cells. German scientists found through experiments that the growth rate of cancer cells will slow down in a noisy environment. This discovery may open up a new way to treat cancer. The Oncology Department of Frejborg Medical College cooperated with the German Music Therapy Research Center in Heidelberg, and successfully conducted a preliminary experiment in this field. Scientists put lung cancer cells cultured in a Petri dish in an environment where a micro-speaker emits a certain regular sound, and found that the growth rate of cancer cells is 20% slower than normal. In order to verify the reliability of the experiment, the scientists also used the magnetic field to affect the cancer cells in another set of test plates by making the speaker silent. Experiments show that the growth rate of this group of cancer cells has not slowed down. Scientists also found through experiments that it is not music with certain significance that can inhibit the growth rate of cancer cells, but "ordinary sound with certain timbre, volume, speed, sound pulse and time interval". At present, German scientists are also considering conducting large-scale experiments to inhibit the growth of tumor cells by using controllable sound stimulation, so as to further verify the reliability and available value of this discovery.
American scientists have recently invented a new thermometer, which can measure temperature through noise. The research report published in the latest issue of Science magazine claims that this instrument can accurately measure the temperature between room temperature and -272. 15 degrees Celsius. Researchers at Yale University made this thermometer out of two layers of aluminum separated by a section of alumina. When a voltage is applied to the instrument, the generated electrons pass through the intermediate interlayer, thus forming a current. The relationship between voltage magnetic field and noise or magnetic difference varies with the temperature in the current. Therefore, this instrument called SNT can measure the temperature as long as the applied voltage is known. Researchers say that SNT can be accurate to one thousandth at -272. 15 degrees Celsius, and its accuracy is five times that of thermometers now used to measure near absolute zero. The biggest advantage of this new design is that it is an original thermometer: no external calibration is needed. This is because the relationship between voltage, noise and temperature only depends on the most basic physical constants. In addition, the accurate temperature measuring range of this instrument is much larger than other thermometers. Therefore, the researchers said that the SNT they developed "may be more widely used than the direct thermometer that is widely used now".
The influence of noise on human beings in different degrees is unbearable: 150dB~ 130dB.
Feeling pain:130dB ~110dB
Very noisy: 1 10dB~70dB.
Mute: 70dB~50dB
Mute: 50dB~30dB
Extremely quiet: 30dB~ 10dB
Mute: 0dB
decibel level
★ 10~20 decibels can hardly be felt.
★ 20~40 decibels is equivalent to speaking softly.
★ 40~60 decibels is equivalent to indoor conversation.
★ 60~70 decibels are harmful to nerves.
★ 70~90 decibels are very noisy. Studying and living in this environment for a long time will gradually destroy human nerve cells.
★ 90~ 100 decibel will damage hearing.
★ 100~ 120 decibels is unbearable, and you can be temporarily deaf in a few minutes.
When the general sound is about 30 decibels, it will not affect normal life and rest. When it reaches above 50 decibels, people will have a great feeling and it is difficult to fall asleep.
Generally, when the sound reaches above 80 decibels, it will be judged as noise.
noise pollution
Noise is caused by natural phenomena (see natural noise) and man-made.
Noise is the sound produced when the generator is irregular. Sound is caused by the vibration of objects and propagates in a certain medium (such as solid, liquid and gas) in the form of waves. Noise pollution usually refers to man-made. From the physiological point of view, any sound that interferes with people's rest, study and work, that is, unnecessary sound, is collectively called noise. When noise has a bad influence on people and the surrounding environment, noise pollution is formed. Since the industrial revolution, the creation and use of various mechanical equipment has brought prosperity and progress to mankind, but at the same time, it has also produced more and more noise.
The editor of this paragraph judges that with the development of modern industry, environmental pollution has also occurred. Noise pollution is a kind of environmental pollution and has become a great harm to human beings. Noise pollution, water pollution and air pollution are considered to be the three major environmental problems in the world.
Noise pollution judgment
Noise is the sound produced when the generator is irregular. Sound is caused by the vibration of objects and propagates in a certain medium (such as solid, liquid and gas) in the form of waves. The sound usually heard is the sound of air. Generally speaking, the frequency of sound waves that the human ear can hear is 20 ~ 20,000,000 Hz, which is called audible sound; Below 20Hz, it is called infrasound; Above 20,000,000 000Hz, it is called ultrasound. The tone of sound depends on the frequency of sound waves. High frequency sounds sharp, while low frequency sounds dull. The volume of sound is determined by the strength of the sound. From the physical point of view, noise is a chaotic and irregular combination of sounds with different frequencies and intensities; Music is a harmonious sound. It is not enough to judge whether a sound belongs to noise only from the perspective of physics, and subjective factors often play a decisive role. For example, beautiful music is music to those who are enjoying it, but it may be noise to those who are studying, resting or concentrating on thinking. Even the same sound, people will have different subjective judgments on the sound in different States and moods, and the sound may become noise or music. Therefore, from the physiological point of view, all sounds that interfere with people's rest, study and work, that is, unnecessary sounds, are collectively called noise. When noise has a bad influence on people and the surrounding environment, noise pollution is formed.
Noise pollution classification
According to the mechanical characteristics of sound source, noise pollution can be divided into: noise caused by gas disturbance, noise caused by solid vibration, noise caused by liquid impact and electromagnetic noise caused by electromagnetic action. Noise can be divided into:: 1000Hz high frequency noise.
Noise can be divided into steady noise, unsteady noise, fluctuation noise, intermittent noise and impulse noise according to its time-varying characteristics.
noise pollution
(1) Traffic noise includes noise generated by motor vehicles, ships, subways, trains and airplanes. Due to the sharp increase in the number of motor vehicles, traffic noise has become the main noise source in cities.
(2) Industrial Noise Noise generated by various equipment in the factory. The sound level of industrial noise is generally high, which has a great impact on workers and surrounding residents.
(3) The construction noise mainly comes from the noise emitted by construction machinery. Construction noise is characterized by high intensity, which mostly occurs in densely populated areas, seriously affecting the rest and life of residents.
(4) Social noise includes people's social activities and noise emitted by household appliances and audio equipment. Although the noise level of these devices is not high, they are closely related to people's daily life, which makes people fidget during rest, which is particularly annoying and easily leads to neighborhood disputes.
Noise pollution prevention and control
In order to prevent noise, Professor Ma, a famous Chinese acoustics scientist, summarized and studied the hazards and standards of various noises at home and abroad, and put forward three suggestions: (1) In order to protect people's hearing and health, the allowable value of noise is 75~90 dB.
(2) Ensure conversation and communication, and the allowable value of environmental noise is 45~60 decibels.
(3) It is recommended to sleep at 35~50 decibels.
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.
Psychologists in China believe that besides human factors, economic and technical feasibility should also be considered in controlling noise environment. Adequate noise control must consider the whole system composed of noise source, sound propagation mode and sound receiver. Noise control measures can be aimed at the above three parts or any of them.
The contents of noise control include:
(1) To reduce the noise of the sound source, industry and transportation can choose low-noise production equipment and improve the production process, or change the motion mode of the noise source (such as damping and vibration isolation to reduce the vibration of the solid sound generator).
(2) Reduce the noise in the sound propagation path, control the noise propagation, change the noise propagation path that has been emitted by the sound source, such as taking measures such as sound absorption, sound insulation, sound barrier and vibration isolation, and rationally plan the layout of cities and buildings.
(3) When the noise protection of the receiver or the receiver fails to take measures in terms of sound source and transmission route, or the acoustic measures still fail to achieve the expected effect, it is necessary to take protective measures for the receiver or the receiver. For example, workers who have been exposed to occupational noise for a long time can wear ear protectors such as earplugs, earmuffs or helmets.
Although noise control is technically mature now, many enterprises and places adopt noise control because of the large scale of modern industry and transportation. Therefore, in the aspect of noise prevention, we must make a comprehensive balance from the aspects of technology, economy and effect. Of course, specific problems should be analyzed in detail. In outdoor, design room, workshop or places where employees work for a long time, the noise intensity should be low; Warehouses or workshops with few people or open places are slightly noisy. In a word, the treatment of noise should be different at different time, place, nature and duration.
Areas that should be strengthened
(1) Strengthen the prevention and control of traffic noise pollution, and fully implement the technical policy for the prevention and control of ground traffic noise pollution. In the elevated roads, expressways, expressways, urban rail and other roads concentrated in noise-sensitive structures (hereinafter referred to as "sensitive areas"), sound barriers will be built, and measures such as no ringing, current restriction and speed limit will be strictly implemented. Accelerate the construction of urban railway crossings to interchanges, and gradually cancel the urban grade crossing. Control the noise pollution of urban high-speed rail operation. Strengthen the prevention and control of noise pollution around the airport and reduce disputes over aviation noise disturbing people.
(2) Strengthen the prevention and control of construction noise pollution, strictly enforce the boundary noise limits of construction sites, and investigate and deal with the excessive emission of construction noise. Strengthen the management of construction noise emission declaration and implement the environmental protection announcement system for urban construction. The people's government of the city shall limit the construction time according to law and strictly limit the construction work that produces noise pollution in sensitive areas at night. Implement the examination and approval management of urban night construction, popularize the automatic noise monitoring system to supervise construction in real time, and encourage the use of low-noise construction equipment and technology.
(three) to promote the prevention and control of noise pollution in social life, strictly implement the community noise emission standards, and prohibit commercial activities from using audio equipment outdoors to attract customers. Strictly control the noise pollution of processing, maintenance, catering, entertainment, fitness, supermarkets and other commercial services, effectively control the noise pollution of cooling towers, elevators, water pump rooms, air conditioners and other supporting service facilities, and strictly manage cultural and sports activities and indoor entertainment activities in sensitive areas. Actively promote the urban indoor comprehensive market and ban the open-air or road market that disturbs people. Strict management of indoor decoration, clearly limit the operation time, and strictly control the decoration operation of noise generated by completed residential buildings. Strengthen the green nursing work during the national examinations such as the senior high school entrance examination and create a good examination environment for candidates.
(4) Deepen the prevention and control of noise pollution in industrial enterprises, implement environmental noise emission standards at the boundary of industrial enterprises, and investigate and deal with noise exceeding the standard to disturb people. Intensify efforts to close pollution sources with excessive noise in sensitive areas. Cities should shut down, relocate and control a number of enterprises with serious noise pollution every year, and realize the noise emission standard of industrial enterprises in sensitive areas before the end of 20 15. Strengthen the prevention and control of noise pollution in industrial parks and prohibit high-noise pollution projects from entering the park. Carry out noise pollution prevention and control in rural industrial enterprises.
Refer to Baidu