一.Types and characteristics of noise

       The types and characteristics of noise are divided into: noise generated by gas disturbance, noise generated by solid vibration, noise generated by liquid impact, and electromagnetic generated by electromagnetic action噪声。噪声按声音的频率可分为：<400Hz的低频噪声 、400～1000Hz的中频噪声及>1000Hz的高频噪声。Noise buttonThe properties of time change can be divided into: steady noise, unsteady noise, fluctuation noise, intermittent noise and pulse noise。    

二.Noise hazard

     1, damage our hearing, long-term under high decibel sound。     

     2, damage to vision, because there is a subtle internal "connection" between the ear and the eye, when the noise acts on the hearing organ, it will also pass through the nervous systemThe use of "spread" visual organs, so that people's vision decline, heavy will make color vision, color field abnormal。     

     3, damage to the cardiovascular system, high blood pressure people under the noise for a long time, will increase the incidence。     

     4, damage the nervous system, affect sleep, long-term in the noise environment, we are easy to anger, upset, affect sleep, easy to appear poor spirit。     
   

        With the development of modern industry, environmental pollution is also produced, noise pollution is a kind of environmental pollution, has become a major harm to human beings。Noise pollutionPollution and air pollution are regarded as three major environmental problems in the world。Noise control, although now technologically mature, has become increasingly difficult due to modern timesThe scale of industry and transportation industry is very large, and there are a large number of enterprises and places to take noise control, so in preventing noise problems, we must focus on technology and economyAnd the effect of the comprehensive balance。    

三.Common methods of noise control

       1, reduce noise in the voice transmission path Reduce noise in the voice transmission path, control the spread of noise, change the noise transmission path that the sound source has issued, such as adoptingSound absorption, sound insulation, sound barrier, vibration isolation and other measures, as well as rational planning of urban and building layout。    

       2, reduce the noise source to reduce the noise source, the industrial and transportation industry can choose low-noise production equipment and improve the production process, or change the noise sourceMode of movement (such as damping, vibration isolation, etc., to reduce the vibration of solid sound)。    

       3, the noise protection of the recipient or the recipient organ, the noise protection of the recipient or the recipient organ, the sound source and the transmission path can not be taken measures, or the sound takenWhen the 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 earsPlugs, earmuffs, or headcovers。