Changes in pitch and strong chaos, the voice sounds discordant
噪音 音高和音强变化混乱，听起来不和谐的声音
Changes in pitch and intensity confusion, it sounds discordant voices. Body by sounds produced by irregular vibrations (as distinct from "musical"). Also refers to noisy, strident voice. Guo Xiaochuan "Angang glance" poem: "That's undulating sound Yeah, not Scream growl noise." Tao "divide welcome": "chaotic noise enveloped the whole station." Ba Jin "explore the set of access Hiroshima ":" quiet night in my second floor hotel window one armchair and sat for a long time, with no noise to interfere, I think a lot of things. "
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No. 2
噪音
噪音
In order to prevent noise China's famous acoustician Professor Ma Taiyou summary and study the hazards and standard of the existing types of noise at home and abroad, put forward three proposals:
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噪音的概念
Physics definition
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Noise Unit
dB (Decibel, dB) is a pure counts, was intended to represent the ratio of the size of two quantities, no units. In engineering applications often see seemingly different definitions way (just look different). For power, dB = 10 * lg (A / B). For voltage or current, dB = 20 * lg (A / B). Here A, B represented in comparing the current value or the power voltage values. dB meaning actually be easier, is to a large (followed by a long string of 0's) or small (in front of a long list of zero) number of relatively brief that out. If (here to power, for example): X = 100000 = 10 ^ 5 X (dB) = 10 * lg (X) dB = 10 * lg (10 ^ 5) dB = 50 dB X = 0.000000000000001 = 10 ^ -15 X (dB) = 10 * log (X) dB = 10 * log (10 ^ -15) dB = -150 dB In general, in the project, between dB and dB only addition and subtraction, multiplication and division no. The most used is the subtraction: dBm dBm is actually two power reduction dividing the signal power and noise power division is the signal to noise ratio (SNR). For example: 30dBm - 0dBm = 1000mW/1mW = 1000 = 30dB. plus dBm dBm is actually two power multiplied, there is no actual physical meaning.
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噪音的产生
Fourth, the combustion noise
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噪音种类及特点
噪音种类及特点
Industrial and commercial establishments such as restaurants and other ventilation systems often generate nuisance noise. Such noise and neighborhood noise, anti-theft alarm, newly registered vehicle noise are subject to supervision of the Noise Control Ordinance, which the noise level must meet the standards of Europe and Japan.
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噪音的分类
71 to 90 dB: severe hearing loss
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噪音的标准值
1.2.3 Ⅲ class standard applies to the industrial zone.
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Noise pollution
噪音的污染
With the development of modern industry, environmental pollution also with produce, noise pollution is a kind of environmental pollution has become a major hazard to humans. Noise pollution and water pollution, air pollution is seen as the world three major environmental problems. No noise is the sound made when issuing rules shedder. Sound vibrations caused by the object, in the form of a wave propagated in a medium (such as solid, liquid, gas) in the. Usually hear the sound of air. Generally, the human ear can hear the sound frequency is 20 ~ 20,000 Hz, is called an audible sound; below 20Hz, called infrasound; higher than 20,000 Hz, is called ultrasound. Hear the pitch of the sound depends on the frequency of sound waves, high-frequency sound sounds sharp, and low frequency sound feels more boring. The size of the sound is the strength of the decision by the sound. From a physical point of view, the noise was from a variety of different frequencies, the sound of different intensity messy combination of erratic made; tones are harmonious sound. Determine whether the voice belonged to a noise, only from the physics point of judgment is not enough, the subjective factors often play a decisive role. For example, the wonderful music for people who are listening to music is a musical, but are learning, rest or concentrate think people may be a noise. Even with one voice, when people in different states, different mood, the sound will produce different subjective judgments, then the sound may become noise or tone. Therefore, from a physiological point of view, people who interfere with rest, learn and voice work that does not require voice, referred to as noise. When the noise adverse impact on people and the surrounding environment, the formation of noise pollution.
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Noise hazards
Noise brings physical and psychological harm on the following main aspects: damage hearing. There are test showed: When people hear the continuous sound of a motorcycle, after eight hours of hearing will be impaired; If the rock concert, half an hour later, people will be hearing impaired. Harmful to the cardiovascular system, Chinese survey of urban noise and the health of residents showed that: noise areas every increase of 1 dB incidence of hypertension increased by 3%. Affect the nervous system, people impatient, irritable. Affect sleep, causing fatigue. From a psychoacoustic perspective, also known as noise noise generally refers to inappropriate or uncomfortable auditory stimuli. It is a composite having a non-periodic sounds and the frequency of vibration of a large number thereof. In short, the noise is aperiodic sound vibrations. Its irregular waveform sonic sounds harsh feel. From the social and psychological sense, all hinder people learn, work and rest and engender a feeling of uncomfortable sounds, called noise. As the sound of water, beat sound, rustle, the roar of machinery, etc., are noise. It is measured in decibels. Zero dB is the lowest intensity audible sound. Noise with high intensity and low intensity of the points. Low-intensity noise in general physical and mental health of the people there is no harm, but in many cases also help improve work efficiency. The main high-intensity noise from industrial machinery (such as weaving machines, lathes, air compressors, picks, blower, etc.), modern means of transport (such as cars, trains, motorcycles, tractors, airplanes, etc.), tweeter, construction sites as well as shopping malls, sports and entertainment venues, such as the noise. These high-intensity noise harm people's body, people feel tired, negative emotions, or even cause disease. High-intensity noise, only damage human hearing, and have varying degrees of impact on the nervous system, cardiovascular system, endocrine system, digestive system and vision, intelligence and so on. If people living in long-term work and 95 dB noise environment, about 29% will lose hearing; Even if only 85 db noise of people, there are 10% of people would deafness occurs; 120 to 130 decibels of noise, can make people feel ear pain; stronger noise causes hearing organ damage. In the nervous system, the noise will make people strong headache, dizziness, fatigue, insomnia, restlessness, memory loss and other syndromes, EEG slow wave increases, the autonomic nervous system dysfunction; in the cardiovascular system, strong noise will makes the pulse and heart rate change occurs, blood pressure, cardiac arrhythmia, conduction block, peripheral blood flow changes; in the endocrine system, strong noise will make people appear hyperthyroidism, adrenal enhanced basal metabolic rate up high, sexual dysfunction, menstrual disorders; in the digestive system, the noise will make people appear strong digestive hypothyroidism, stomach disorders, gastric acid reduction, loss of appetite. In short, strong noise causes the body to a series of physiological and pathological changes. Some 202 people had to work up to 95 db in noise environment conducted surveys, dizziness, accounted for 39%, accounting for 32% of insomnia, headaches, 27%, 27% stomach, accounting for 27% of flustered, memory recession accounted for 27%, accounting for 22% of the up_set_, poor appetite, 18%, 12% hypertension. Long-term pregnant women over 50 db noise in the environment, make the endocrine glands dysfunction and mental stress and endocrine system disorders. Causes severe high blood pressure, fetal hypoxia ischemia, leading to miscarriage or fetal malformation. The high-decibel noise can damage the fetal auditory organs, resulting in some of the affected area. Affect brain development, resulting in children with mental retardation. Malignant stimulus noise, seriously affecting the quality of our sleep and can cause dizziness, headache, insomnia, dreams, memory loss, inability to concentrate, nausea and other symptoms of neurasthenia, Yu Tu, stomach pain, bloating, loss of appetite and other gastrointestinal sluggish symptoms. Nutritionists study found that noise can make the body of vitamins, trace elements amino acid consumption, Valley nitric acid, nitric acid, etc. must rely on nutrients increases affect health; noise makes the adrenal glands increased heartbeat, increased blood pressure, easily lead to a heart attack; make noise while human saliva, gastric secretion, reduce gastric acid, thus suffering from gastric ulcer and duodenal ulcer.
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噪音对人体健康的影响
Fifth, the psychological impact of noise on
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噪音的防止方法
噪音的防止方法
(1) to create a soundproof forest
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噪音的利用
Noise medical consultation wonderful, sweet music can heal, which has been known to everyone. But the noise how it can be used for medical consultation? Recently, scientists prepare a diagnostic laser hearing device, which comprises a light source, the noise generator and computer test consists of three parts. When used, it first by micro-noise generator short faint noise, vibration eardrum, and then micro-computers will be based on the echo, the eardrum functional data displayed for doctors to diagnose. It tests quickly, will not damage the eardrum, no pain, especially for children. In addition, you can also use noise thermometry to detect human lesions. Active Noise is usually used three kinds of noise reduction measures, namely the sound source at the noise, noise in the communication process and at the noise in the human ear, are passive. In order to proactively eliminate noise, people invented the "Active Noise Control," this technology. Its principle is: All of the sound by a certain spectral composition, if you can find a voice, to eliminate the spectrum and the noise exactly the same, just the opposite phase (difference of 180 °), the noise can be completely off_set_ these . The key lies in how to get that off_set_ the noise sound. The approach is practical: to proceed from the noise source itself, trying to pass the electronic circuit of the phase noise of the original upside down. Seen in this light, active noise this technology actually "fire with fire."
