NOISE

From Big Medical Encyclopedia

NOISE, influence on opr of An and z m of III. — a chaotic combination various on force and frequency of sounds; it is capable to make an adverse effect on an organism.

Sh.'s source is any process causing local change of pressure or mechanical oscillations in firm, fluid and gaseous media. Y. has a certain frequency, or the range expressed in hertz and intensity — the level of sound pressure measured in decibels (see Units). For the person the area of the heard sounds is defined in the range from 16 to 20 Ltd companies of Hz. Range of the levels of sound pressure perceived by an ear stretches of 2-10 "5 to 2 - 102 N/sq.m.

Measurement, analysis and registration of a range of III. spetsial-nykhm by devices — audio-noise meters and auxiliary devices are made (recorders of levels Sh., the tape recorder, an oscillograph, analyzers of statistical distribution, dosimeters, etc.). As the ear is less sensitive to low and is more sensitive to high frequencies, for obtaining the indications corresponding to perception of the person in audio-noise meters use system of the adjusted frequency characteristics — scales of A, B, C, D and a linear scale, to-rye differ on perception. The scale is in practice applied generally And.

The normalized parameters Sh. are levels of sound pressure in octava strips with compound frequencies of 63, 125, 250, 500, 1000, 2000, 4000 both 8000 Hz and equivalent (on energy) the level of a sound in decibels (a scale And). Tolerance levels of Sh. in workplaces do not exceed respectively 110, 94, 87, 81, 78, 75, 73 dB, and on a scale And — 80 dB.

Highway — one of the most widespread adverse physical environmental factors gaining important sotsialnogigiyenichesky value in connection with an urbanization, and also mechanization and automation tekhnol. processes, further development of diesel engine manufacturing, reactive aircraft, transport. E.g., at start of jets of airplanes level Sh. fluctuates from 120 to 140 dB, at a staff-wood and the cabin of sheet steel — from 118 to 130 dB, operation of woodworking machines — from 100 to 120 dB, looms — to 105 dB; the household noise connected with life activity of people makes 45 — 60 dB.

For a gigabyte. Sh.'s estimates subdivide: on character of a range — on broadband with a continuous spectrum more than one wide an octave and tone, in a range to-rogo are available discrete tone; on spectral structure — on low-frequency (the maximum of sound energy is the share of frequency below 400 Hz), mid-frequency (a maximum of sound energy at frequencies from 400 to 1000 Hz) and high-frequency (a maximum of sound energy at frequencies over 1000 Hz); according to temporary characteristics — on constant (level of a sound changes in time no more than on 5 dB — on a scale And) and non-constant. Treat non-constant Sh. fluctuating III., at Krom the level of a sound continuously changes in time; discontinuous Sh. (level of a sound remains to constants during an interval lasting 1 sec. and more); the pulse Sh. consisting of one or several audibles signal lasting less than 1 sec.

Long impact of Sh. on a human body leads to development of the exhaustion (see) which is quite often turning into overfatigue to decline in production and qualities of work. Especially adversely Sh. affects an acoustic organ, causing damage of a cochlear nerve (see. Before a door and cochlear nerve) with gradual development of relative deafness (see). As a rule, both ears suffer to the same extent. Initial manifestations of professional relative deafness, according to the International Organization for Standardization (1971), most often occur at persons with length of service in the conditions of noise apprx. 5 years. The risk of a hearing loss at Sh. working at the ten-year duration of influence makes 10% at the level of 90 dB (a scale And), 29% — at 100 dB

(a scale And) and 55% — at 110 dB (a scale And). The sound irritation is followed by emergence of the changes observed in all links and elements of the sound perceiving department of acoustical system.

Nonspecific influence of III. it is usually shown earlier, than changes in an acoustic organ, and it is expressed in disturbances of the psychological sphere in the form of the neurotic and asthenic syndromes in combination with vegetative dysfunction which are followed by irritability, the general weakness, a headache, dizziness, increased fatigue, frustration of a dream, easing of memory, etc. (see. Asthenic syndrome). Decrease or increase in tendon and periosteal jerks on hands and legs, a tremor of fingers of outstretched arms, a poshatyvaniye in Romberg's pose, a distal hyperhidrosis, a bright resistant dermographism is objectively noted. The possibility of development of a neurocirculatory syndrome is not excluded, it is preferential on hypertensive type. At the persons which are affected by III., changes of secretory and motor functions can be also observed went. - kish. a path, shifts in exchange processes — disturbance of the main, vitamin, carbohydrate, proteinaceous, fatty and salt exchanges, disturbances of a functional condition of cardiovascular system in the form of bradycardia, increases in a tone of peripheral vessels, etc.

Under production conditions Sh.'s influence on working usually is combined with some other adverse factors — the vibration (see) determined by degree of tension and weight of work, unsatisfactory microclimatic conditions (see the Microclimate), influence of chemical substances, an infrasound (see) and ultrasound (see), the electromagnetic field (see) etc. The combined Sh.'s action and various physical and volumetric factors on a human body is studied insufficiently. Highway can aggravate an adverse effect of concurrent factors of the physical and chemical nature, exerting first of all negative impact on the state of health and efficiency of professional groups, work to-rykh is followed by nervous tension. It is proved that Sh. and tension of work are biologically equivalent on the impact on a nervous system. On the example of studying of different professions size fiziologo-gigiyeniche-skogo Sh.'s equivalent and tension of neuroemotional work is established, edges there are in limits 7 — 13 dB (a scale And) on one category of tension.

Effective protection of Sh. working from adverse influence demands implementation of a complex of organizational, technical and medical measures at design stages, construction and operation of manufacturing enterprises, cars and the equipment. For increase in efficiency of noise control of M3 of the USSR are entered an obligatory gigabyte. control of the objects generating noise, registration of the physical factors making harmful effects on the environment and negatively influencing human health.

An effective solution of a problem of fight against Sh. is decrease in its level in the source due to change of technology and a design of cars. Treat measures of this type replacement of noisy processes silent, percussions — unaccented, napr, replacement of a staff-wood — the soldering, forging and stamping by processing by pressure; replacement of metal in nek-ry details not sonorous materials, use of vibration insulation, mufflers, damping, the soundproofing casings, etc. At impossibility of decrease in Sh. the equipment which is a source of the raised Sh. is installed to special rooms, and the remote control is placed in the quiet room. In nek-ry cases decrease in level Sh. is reached by use of the sound-absorbing porous materials covered with perforated sheets of aluminum, plastic. In need of increase in coefficient of a sound absorption in the field of high frequencies acoustical blankets cover with a protective shell with small and frequent perforation, apply also piece sound absorbers in the form of the cones, cubes fixed over the equipment which is a source of the raised Highway. In fight against Sh. arkhitekturnoplanirovochny and construction actions are of great importance. When technical ways do not provide achievement of requirements of the existing standards, restriction of duration of influence of Sh. and use of antinoise is necessary (see). Working in the conditions of intensive Sh. are subject to preliminary and periodic medical examinations (see. Medical examination) for the purpose of identification of contraindications for the work connected with noise and early forms of the prof. of pathology.

Bibliography: And N d p e e in and - and l and N and -

N and E. Ts., etc. Noise and noise disease, L., 1972, bibliogr.; Suva

ditch G. A. and Likhnitsky A. M. Pulse noise and its influence on a human body, L., 1975, bibliogr.; With at - G. A. thieves, Shkari L. N. and Denisov E. I. is new. Hygienic rationing of production noise and vibrations, M., 1 984. G. A. Suvorov.

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