Noise - random combination of different power and frequency sounds. Sound as a physical phenomenon is a wave-like motion in an elastic medium, is called oscillatory movements sounding of the body and the perceived authority of the hearing of the person and animals. The physical side, the sound is characterized by the level of sound pressure, measured in decibels, and the oscillation frequency, expressed in Hertz (Hz to 1 cycle per second). The person perceives the sound vibrations with a frequency of 16 to 20 000 Hz. Power sound pressure is not completely determines the degree of perception by the organ of hearing, as nervous apparatus of the inner ear, perceiving the sound that is more sensitive to high frequency sounds. To compare the degree of perception of different frequency sounds introduced a special unit of loudness- "background" level standard tone with a frequency of 1000 Hz, power sound pressure is equal to 1 dB).
Measurement of noise level produced by the special devices - sound level meters. Determination of the noise spectrum (frequency components of its sounds, and part of the overall sound energy falling on separate frequencies) is made by means of spectrum analyzers noise.
Noise has on the human body adverse effect and may cause a different kind of painful conditions, including hearing loss (see) and deafness. Under the influence of noise increased heart rate and breathing, increased energy consumption. Prolonged exposure to noise harmful effect on the Central nervous system and the human psyche. In the result of noise exposure in humans the symptoms of fatigue and exhaustion of the nervous system. On the part of the psyche is observed depressed mood, decrease of attention, delayed intellectual processes, increased nervous anxiety. Noise reduces efficiency and productivity, preventing the normal rest and disrupts sleep. Under the influence of noise considerable forces there are variations of the normal activity of various organs and systems (the change in the secretion of gastric juice, high blood pressure and so on).
Activities to combat noise in the settlements are: rational planning, landscaping, ordering traffic, replacement noisy town transport less noisy, prohibition of sound signals of transport, soundproofing residential buildings, noise reduction built-in building engineering equipment (elevators, pumps, motors, fans and so on), the limitation of household noises. Measures to reduce or eliminate the noise in the production are: change of the technological process, Chemometrics control of new kinds of industrial equipment, soundproofing production premises with noisy processes and sources of noise, the use of sound-absorbing building materials, supervision of the working equipment. Machines that produce noise, mounted on a special Foundation, separated from the other structures air layers of elastic materials. In the bustling shops of used means of individual protection of workers (see Proteosome). Working bustling shops undergo a preliminary medical examination by a neurologist, an ENT specialist and a physician. Contraindications are consistent reduction in hearing, internal diseases and, in some cases, the middle ear, organic diseases of the Central nervous system and diseases of the cardiovascular system.
The requirements for the noise level is determined according to the Hygienic norms of acceptable levels of sound pressure and sound levels at working places № 1004-73 (adopted by the Chief San. doctor of the USSR 12/1 1973) and Sanitary norms of acceptable noise in residential and public buildings and on the territory of the dwelling building № 872-70.

Noise (noise) - erratic nonperiodic oscillations of different physical nature.
Noise contain almost all of the audible frequency range from 16 to 20 000 Hz, but with a different allocation of their intensities, and also the unequal nature of the changes over time of the total intensity.
The intensity of the noise appreciate the attitudes generated sound pressure to the pressure taken per unit of comparison [2x10-5 n/m2 (Newton per square meter) ], which corresponds approximately to the threshold of perception by the human ear tone with a frequency of 1000 Hz.
As the ratio of the sound pressure from the threshold of perception (2·10-5 n/m2) to the threshold of pain (20 n/m2) change millions of times, it is customary to measure the intensity of noise in logarithmic units - dB, which significantly reduces measurement scale. In practice the measurement scale is limited by the range from 20 to 140 dB. A set of frequency components of the noise that is called the spectrum of the noise.
The nature of changes in the total intensity in time noise divided into stable intensity in time no more than 5 dB in the pulse (drums) with the sharp rise and subsequent decline of intensity.
Width of the spectrum are distinguished: a narrow-band noise, consisting of a limited number of adjacent frequency and broadband, which includes almost all the audible frequency range. The predominance of intensity in the spectrum in the frequency range of 300 Hz noise is considered low, over 1000 Hz frequency, from 300 to 1000 Hz mid-frequency. Time noise impact on the human body are distinguished: long acting within 4 hours and more, and noise short - less than 4 hours per working shift. Measure the noise with the help of sound level meters - devices that define the overall intensity of the noise. United with them octave or more narrow filters can measure the intensity in the separate sound ranges, due to what is determined by the range of different noises.

Sources of noise at work is the equipment: machines with electric, pneumatic and motorized actuators, lifting-transport mechanisms; supporting engineering equipment, compressors, pumps, fans, transformers, as well as technological operations on processing of materials. The most bustling areas industries are: mechanical engineering - chipping areas foundry, stamping and forging shops, workshops testing of all types of engines, richtofen-tapping areas of training workshops, Assembly shops with areas pneumatic riveting, ball mills bearing plants; metallurgical industry - hardware production; in the forest industry and woodworking shops; in textile industry - weaving workshops, especially with the Shuttle looms.
Noise is a biological stimulus acting on all organs and systems mainly through the auditory analyzer on the Central nervous system.
Exhaustive characteristics of noise are urovnyami noise, showing the change of energy of oscillatory process in time, and spectrogram noise that indicates the distribution of energy fluctuations over the frequency range in a given time.
The ear is most sensitive to high frequency sounds (over 1000 Hz), which cause the earliest tired of hearing and violation of relations of the basic processes in the Central nervous system. Prolonged exposure to noise on the body may lead to professional hearing loss (see Acoustic trauma, Hearing loss) and the General disorders (hypertension, hypotension, heartburn, headache, and others), as well as escalating chronic diseases.
The struggle with industrial noise is a national task.
Active in the USSR State sanitary rules on the limitation of noise production is permitted noise levels in the workplace, which should be considered when designing machines and other equipment and in industrial areas. No less important element in the prevention of harmful effects of noise is the oversight of existing machinery and equipment, identification of sites and shops with noise levels exceeding permissible, and the development of prophylactic measures to reduce noise at the workplace.
The greatest effect in the complex prevention give technical means noise control, namely: reduction of noise at source of his education constructive, technological and operational measures; reduction of noise on the way of its dissemination by means of sound insulation and sound absorption.
In the absence of technical possibilities to reduce noise to safe limits use personal protection from noise - proteosome (see)that when choosing the right type and systematic use significantly reduces the risk of adverse noise impact on the body.
Measures for health prevention in the fight against noise are preliminary and periodic medical examinations of persons working in the conditions of noise; in particular, provides professional selection (see) when applying for a job and early diagnosis of possible disorders from the action of noise.
Properly designed complex of all measures (technical, medical, organizational can completely prevent the harmful effects of noise on the body.