Noise and vibrations exceeding the loudness and sound frequency limits are occupational hazards. Noise is a combination of sounds of varying intensity and frequency, which has an irritating and harmful effect on the human body. Under the influence of noise, a person's blood pressure may change, work gastrointestinal tract, and its prolonged action in some cases leads to partial or complete hearing loss. Noise affects the productivity of workers, weakens attention, causes hearing loss and deafness, irritates the nervous system, as a result of which the susceptibility to danger signals is reduced, which can lead to an accident.

Noise is distinguished Shock(forging, riveting, stamping, etc.), Mechanical(friction and beating of units and machine parts), Gas and Hydrodynamic(noise in apparatus and pipelines at high speeds of air, gas and liquid movement).

Noises are classified according to the nature of the spectrum (into broadband, with a continuous spectrum more than one octave wide; tonal, in the spectrum of which there are audible discrete tones); by time characteristics (for constant, the sound level of which over an 8-hour working day changes in time by no more than 5 dB when measured on the time characteristic of a "slow" sound level meter according to GOST 17187-71; non-constant, the sound level of which during an 8-hour working day the day changes in time by at least 5 dB when measuring the time characteristic of the "slow" sound level meter according to GOST 17187-71).

In addition, intermittent noises are classified into:

· Oscillating in time, the sound level of which is continuously changing in time; intermittent, the sound level of which drops sharply to the level of background noise;

· Pulse, consisting of one or several sound signals each with a duration of less than 1 s, while the sound levels in dB when the characteristics "slow" and "impulse" of the sound level meter according to GOST 17187-81 differ by at least 10 dB.

Constant noise in workplaces is characterized by levels sound pressure in octave bands (in dB) with geometric mean frequencies 63, 125, 250, 500, 1000, 2000, 4000, 8000 Not determined by the formula

Where: P is the root-mean-square value of the sound pressure, Pa;

Po- 2-10-5-threshold value of the root-mean-square sound pressure, Pa.

When measuring noise on the A scale, sound level meters in accordance with GOST 17187-81 R accept as Ra, determined from the root-mean-square value of the sound pressure, taking into account the correction A sound level meter (in Pa).

The characteristic of intermittent noise at workplaces is the equivalent (in terms of energy) noise level (in dB), determined in accordance with GOST 20445-75.

The minimum sound intensity that is perceived by the human ear is called Threshold of audibility. The greatest sound power, exceeding which leads to a sensation of pain, is called Pain threshold. The range of sounds perceived by the human ear is within the 0 ... 130 dB scale. The lower limit of the scale corresponds to the hearing threshold, the upper one - to the pain threshold. Noise with a level of 130 ... 150 dB can cause mechanical damage to the hearing organs. The harmless (reference) level of the highest noise volume for a person is 70 dB (at an oscillation frequency of 1000 Hz).

By its physical nature, vibration, just like noise, is the vibrational motion of material bodies with frequencies in the range of 12 .-. 8000 Hz, perceived by a person during his direct contact with vibrating surfaces.

Vibration - vibrations of parts of production equipment and pipelines arising from unsatisfactory fastening, poor balancing of moving and rotating parts of machines and installations, work, shock mechanisms, etc. Vibration is characterized by the frequency (T-1) of vibrations (in Hz), amplitude ( in mm or cm), acceleration (in m / s). At a frequency of more than 25 Hz, vibration has an adverse effect on the nervous system, which can lead to the development of severe nervous disease- vibration disease.

By analogy with noise, the vibration intensity can be measured in relative values ​​- decibels and characterized by:

The level of vibrational speed according to the formula

Where:V- vibrational speed, cm / s;

Vo- the threshold value of the vibrational velocity, taken as a unit of comparison and equal to 5 * 10-5 cm / s at a sound pressure P = 2-10-5 Pa and a displacement amplitude of 8 * 10-10 cm;

The level of vibrational acceleration according to the formula

Where: a - vibrational acceleration, cm / s2;

a0, is the threshold value of the vibrational acceleration taken as a unit of comparison and equal to 3 * 10-2 cm / s2 at sound pressureP= 2 * 10-5 Pa and a displacement amplitude of 8 * 10-10 cm.

Among the harmful works in construction, which generate noise and vibration (shaking), include work associated with the use of manual pneumatic machines, vibrators, parquet planing and grinding machines, work on driving piles, loosening frozen soil, etc. Vibration is distinguished - general and local. The general includes vibration of a structure or unit on which a person is located. Local vibration arises from a hand-held machine in the hands of a worker, or an element of a machine.

Maximum permissible levels of general vibration set for speed in both absolute and relative values ​​over a frequency spectrum including six octave frequency bands; with geometric mean values ​​of frequencies 2; 4; eight; 16; 31.5 and 63 Hz with an amplitude of displacement at harmonic vibrations of 3.11 ... 0.005 mm and an rms value of the vibrational speed of 11.2 ... 2 mm / s. The maximum permissible values ​​of local vibrations at a rotational speed of 1200-6000 min are 20-100 Hz with an oscillation amplitude of 1.5-0.005 mm.

The sound pressure level is measured by sound level meters: type Ш-63 (IRPA), Ш-ЗМ, ISHV (with a sound pressure level measurement interval of 30 ... 140) and noise spectrum analyzers ASh-2M, PF-1, 0-34 (with a measurement interval of 40 ... 10000). The most widespread sound level meter is the Sh-ZM type. The device is designed to measure the sound pressure level and noise levels. Local vibration is determined using low-frequency (with a vibration measurement interval of 1.4 ... 350) and vibration measuring equipment (with a measurement interval of 70 ... 130) vibrographs NVA-1, VIP-2. The general vibration, amplitude and frequency of vibration (vibration of structures on which a person is located) are measured with electronic devices VEP-4, VI6-5 MA, K.001 in conjunction with oscilloscopes N-700, N-004, etc. The main recording mechanism in the device is vibration sensor of seismic type VD-4. During the measurement, the sensor is placed on a vibrating surface.

It should be noted that the fight against noise and vibration is a complex problem that affects the interests of many specialists, builders, designers, doctors and acoustics. General and individual means are used to protect against noise and vibration.

TO General remedies These include, first of all, the improvement of construction machines and the technological process (for example, replacing riveting with electric welding), the layout of industrial premises and the isolation of noisy production processes, the use of sound-insulating and sound-absorbing materials in machines, walls, ceilings and partitions. An effective means of protection against the propagation of noise is to cover the machine with a casing made of sound-absorbing materials (such as noise mufflers) and switch to remote control of vibro-pneumatic processes. Areas with sound levels above 85 dB must be marked with safety signs, and workers must be provided with personal protective equipment. No people are allowed in areas with octave sound pressure levels above 135 dB.

All kinds of protective devices, vibration isolating, vibration damping and vibration damping devices for automatic control, signaling and remote control can be referred to the means of protection against vibration.

TO Personal protective equipment, from the harmful effects of noise include anti-noise, helmets, earphones, earbuds, and from the effects of vibration - the use of vibration-damping shoes, special gloves and mittens (when using hand-held vibrators).

The impact of ultrasound (during mechanical processing of materials, welding, tinning, etc.) on the human body occurs through the air and directly when a person comes into contact with objects. The physiological effect of ultrasound causes a thermal effect (temperature increase) and variable pressure in human tissues, as well as rapid fatigue, ear pain, upsets the balance and develops neurosis and hypotension.

The means of eliminating and reducing the harmful effects of ultrasound also include constructive and planning solutions aimed at its localization. This is the use of soundproof casings, half-housings, screens, placement of equipment in separate rooms and offices, the device of a blocking system that turns off the generator of the ultrasound source in case of violation of sound insulation, the use of remote control, lining of individual rooms and cabins with sound-absorbing materials.

Organizational and preventive measures to protect against harmful effects elevated levels include instructing workers on the nature of the action of ultrasound and rational modes of work and rest.

Industrial noise

Noise is the name for sounds adversely affecting a person. Sound as a physical phenomenon is a wave motion of an elastic medium. Noise is thus a collection of audible sounds of varying frequency, irregular intensity and duration.

For a normal existence, in order not to feel isolated from the world, a person needs a noise of 10-20 dB. This is the noise of foliage, park and forest. The development of technology and industrial production is accompanied by an increase in the level of noise affecting humans. Silent production facilities practically do not exist, however, noise as an occupational hazard is of particular importance in cases of its high intensity. A significant level of noise is observed in the mining industry, in mechanical engineering, in the logging and woodworking industries, in the textile industry.

Under industrial conditions, the impact of noise on the body is often combined with other negative effects: toxic substances, temperature changes, vibration, etc.

Oscillatory disturbances propagating from a source in the environment are called sound waves, and the space in which they are observed is called a sound field. A sound wave is characterized by sound pressure. Sound pressure P is the time average overpressure on an obstacle placed in the path of the wave. At the threshold of audibility, the human ear perceives sound pressure P 0 = 2 10 -5 PA at a frequency of 1000 Hz; at the threshold of pain, the sound pressure reaches 2 10 2 PA.

For practical purposes, a convenient sound characteristic, measured in decibels, is the sound pressure level. The sound pressure level N is the ratio of the given sound pressure P to the threshold pressure P 0 expressed on a logarithmic scale:

N = 20 lg (P / P 0) (1)

Sound levels are measured with sound level meters to evaluate various noises. In the sound level meter, the sound received by the microphone is converted into electrical vibrations, which are amplified, passed through filters, straightened and recorded by a pointer device.

Loudness and volume are used to assess the physiological effects of noise on humans. The hearing threshold changes with frequency, decreases with increasing sound frequency from 16 to 4000 Hz, then increases with increasing frequency up to 2000 Hz. For example, a sound that produces a SPL of 20 dB at 1000 Hz will have the same loudness as a sound of 50 dB at 125 Hz. Therefore, the sound of the same volume level at different frequencies has a different intensity.

By its nature, noise is classified into:

1.noise of mechanical origin - noise arising from vibration of surfaces of machines and equipment, as well as single or periodic shocks in the joints of parts, assembly units or structures in general;

2.noise of aerodynamic origin - noise arising from stationary or non-stationary processes in gases (outflow of compressed air or gas from holes; pressure pulsation when air or gas flows in pipes, or when bodies move in air at high speeds, combustion of liquid and atomized fuel in nozzles, etc.);

3. noise of electromagnetic origin - noise arising from vibrations of elements of electromechanical devices under the influence of variable magnetic forces (vibrations of the stator and rotor of electrical machines, transformer core, etc.);

4. noise of hydrodynamic origin - noise arising from stationary and non-stationary processes in liquids (hydraulic shocks, flow turbulence, cavitation, etc.).

Whenever possible, noise propagation is divided into:

1. airborne noise - noise spreading in the air from the source of origin to the place of observation;

2. structure-borne noise - noise emitted by the surfaces of vibrating structures of walls, ceilings, partitions of buildings in the audio frequency range.

By frequency, sound vibrations can be classified as follows:

Less than 16-21 Hz - infrasound;

From 16 to 21,000 Hz - audible sound (16-300 Hz - low frequency);

350 - 800 Hz - mid-frequency;

800 - 21,000 Hz - high frequency;

Above 21,000 Hz - ultrasound.

A person perceives sound vibrations with a frequency of 16 to 4000 Hz. The human ear does not perceive infrasound and ultrasound.

By the nature of the noise spectrum, there are:

Tonal noise in the spectrum of which there are pronounced tones. The tonal nature of the noise for practical purposes is established by measuring in one-third octave frequency bands by the excess of the level in one band over the adjacent ones by at least 10 dB.

In terms of time characteristics, noise is subdivided into:

Constant noise, the sound level of which during an 8-hour working day or during the measurement in the premises of residential and public buildings, in the territory of residential buildings, changes in time by no more than 5 dB when measured on the time characteristic of the sound level meter "slowly";

Intermittent noise, the level of which during an 8-hour workday, work shift or during measurement in residential and public buildings, in a residential area, changes over time by more than 5 dB when measured on the time characteristic of the sound level meter "slowly".

Intermittent noises, in turn, can be divided into:

Time-varying noise whose sound level continuously changes over time;

Intermittent noise, the sound level of which changes stepwise (by 5 dB or more), and the duration of the intervals during which the level remains constant is 1 s or more;

Impulse noise, consisting of one or more sound signals, each with a duration of less than 1 s, measured in the "impulse" and "slow" time characteristics, respectively, differ by at least 7 dB.

The reasons for the occurrence of high noise levels of machines and units can be:

a) design features machines, which result in shocks and friction of units and parts: for example, impacts of pushers on valve stems, operation of crank mechanisms and gear wheels, insufficient rigidity of individual parts of the machine, which leads to its vibrations;

b) technological shortcomings that appeared in the process of manufacturing equipment, which can be attributed to: poor dynamic balancing of rotating parts and assemblies, inaccurate implementation of the gearing step and the shape of the tooth profile of the gear wheels (even negligible deviations in the dimensions of machine parts are reflected in the noise level);

c) poor-quality installation of equipment at production areas, which leads, on the one hand, to distortions and eccentricity of working parts and machine units, on the other, to vibrations of building structures;

d) violation of the rules for the technical operation of machines and units - incorrect operation of the equipment, i.e. a mode that differs from the nominal (passport), inappropriate maintenance of the machine park, etc.;

e) untimely and poor-quality scheduled preventive maintenance, which leads not only to a deterioration in the quality of the mechanisms, but also contributes to an increase in production noise; timely and high-quality repairs, replacement of worn-out equipment parts prevent an increase in distortions and backlash in the moving parts of mechanisms, and, consequently, an increase in the noise level at workplaces;

When placing noisy equipment, the "sonority" of the room should be taken into account, depending on the shape, size, wall decoration. There are cases when these features of the room lead to lengthening the duration of the sound due to the multiple reflection of sounds from the surfaces of the floor, ceiling, walls. This phenomenon is called reverberation. The fight against it must be taken into account in the design of industrial workshops in which it is planned to install noisy equipment.

Human exposure to noise

A person perceives noise with an auditory analyzer - an organ of hearing, in which the mechanical energy of stimulation of the receptor is converted into sensation, the greatest sensitivity is observed in the frequency range from 800 to 4000 Hz.

Hearing acuity is not constant. In silence, it increases, under the influence of noise, it decreases. This temporary change in the sensitivity of the hearing aid is called hearing adaptation. The adaptation plays a protective role against continuous noise.

Long-term exposure to high-intensity noise leads to a pathological state of the auditory organ, to its fatigue.

The psychophysiological perception of a signal with a constant level of intensity over the entire frequency range is not the same. Since the perception of a signal equal in strength changes with frequency, a frequency of 1000 Hz was chosen for the reference comparison of the loudness of the signal under investigation. The decrease in hearing sensitivity in a person in noisy industries depends on the intensity and frequency of sound. So, the minimum intensity at which the exhausting effect of noise begins to manifest itself depends on the frequency of sounds entering it.

The appearance of fatigue of the organ of hearing should be considered as an early signal of the threat of the development of hearing loss and deafness. The syndrome of auditory receptor disease is headaches and tinnitus, sometimes loss of balance and nausea.

It was found that the degree of decrease in auditory sensitivity is directly proportional to the time of work in a noisy production environment. The individual sensitivity of the organism to noise exposure is of great importance. Thus, high-frequency noise with a sound pressure level of 100 dB causes signs of hearing loss in some people in just a few months, in others after years.

Noise in the workplace leads to rapid fatigue of workers, and this leads to a decrease in concentration and an increase in rejects. Intense noise causes changes in the cardiovascular system, accompanied by a violation of the tone and rhythm of heart contractions. Arterial blood pressure in most cases changes, which contributes to general weakness organism. Changes in the functional state of the central nervous system are also observed under the influence of noise. It also depends on the intelligibility of speech in a noisy production environment, since illegible speech also has a negative effect on the human psyche.

Noise protection

Protection of workers from high level noise is achieved by limiting the permissible level of exposure, using collective means (reducing noise at the source and along the path of its propagation) and individual protection. The means of collective protection, depending on the method of implementation, can be acoustic, architectural and planning and organizational and technical.

Methods for noise reduction in industrial premises:

Reducing the noise level at the source;

Reducing the noise level along the path of propagation (sound absorption and sound insulation);

Installation of noise mufflers;

Rational placement of equipment;

The use of personal protective equipment;

Medical and preventive measures.

Most effective technical means reducing noise at the source of occurrence:

Change of types of movements of mechanisms, materials, coatings;

Mass and stiffness separation;

Balancing rotating parts, etc.

Reducing noise is achieved by installing sound-insulating and sound-absorbing screens, partitions, casings, cabins. Reducing noise by sound absorption is a transition of vibrational energy of waves into thermal energy by overcoming friction in the pores of the material and dissipating energy in the environment. For sound insulation, the mass of the fences, the density of the material (metal, wood, plastic, concrete, etc.), and the design of the fence are of great importance. The best sound-absorbing properties are provided by porous lattice materials (glass wool, felt, rubber, foam rubber, etc.).

Individual protection means.

To protect workers, earplugs, headphones, headsets, etc. are used. Earbuds and headphones are sometimes built into helmets and helmets. The earmolds are made of rubber, elastic materials, rubber, ebonite and ultra-fine fiber. When using them, a decrease in the sound pressure level by 10-15 dB is obtained. Headphones reduce the sound pressure level by 7-35 dB in the middle frequency range. Headphones protect the parotid region and reduce the sound pressure level by 30-40 dB in the middle frequency range.

Medical and prophylactic means include: the organization of the work and rest regime, strict control over its implementation; medical monitoring of the state of health, therapeutic and prophylactic measures (hydrotherapy, massage, vitamins, etc.)

Vibration

Scientific and technological progress in industry predetermines the widespread introduction of vibration technology, which is explained by the high productivity and significant economic efficiency of vibration machines.

Vibration is small mechanical vibrations that arise in elastic bodies or bodies under the influence of an alternating physical field.

The sources of vibration are reciprocating moving systems (crank presses, vibration-forming units, planting machines, etc.), unbalanced rotating masses (grinding machines and machines, turbines, mill winders). Sometimes vibrations are created by shocks when air, liquid moves. Vibrations are often caused by imbalances in the system; inhomogeneity of the material of a rotating body, mismatch between the center of mass of the body and the axis of rotation, deformation of parts from uneven heating, etc. Vibration is determined by the parameters of frequency (Hz), displacement amplitudes, velocity and acceleration.

The effects of vibrations on humans are classified:

By the method of transmitting vibration to a person;

In the direction of vibration;

By the time of action.

By the method of transmission per person, it is subdivided into:

1. common, transmitted through the supporting surfaces to the body of a sitting or standing person.

2. local, transmitted through human hands. It includes the impact on the legs of a seated person and on the forearms in contact with vibrating surfaces.

The general production vibration by the source of its occurrence and the possibility of regulating its intensity by the operator is divided into the following categories:

Category 1 - transport vibration affecting a person at the workplaces of mobile machines and Vehicle when they move on terrain or roads (including during their construction). This includes jobs on tractors and self-propelled machines for soil cultivation, harvesting and sowing crops, trucks, road construction machines, snow plows, self-propelled mining rail transport.

Category 2 - transport and technological vibration affecting a person at the workplaces of machines with limited mobility when moving them over specially prepared surfaces of industrial premises, industrial sites and mine workings. It includes jobs on excavators, construction cranes, machines for loading open-hearth furnaces in metallurgical production, mining combines, mine loaders, self-propelled drill carriages, track machines, concrete pavers, floor-standing industrial vehicles.

Category 3 - technological vibration affecting a person at workplaces of stationary machines or transmitted to workplaces that do not have sources of vibration. It includes jobs at metal and woodworking machines, forging and pressing equipment, foundry machines, electric pumping units, etc.

Local vibration according to the source of occurrence is subdivided into transmitted from:

Manual machines with motors or manual power tools, manual controls of machines and equipment;

Hand tools without motors (for example, straightening hammers of different models) and workpieces.

According to the direction of action, vibration is subdivided into:

Vertical, extending along the x-axis perpendicular to the supporting surface;

Horizontal, extending along the y-axis, from back to chest;

Horizontal, extending along the z-axis, from the right shoulder to the left shoulder.

Vertical vibration is especially unfavorable for those working in

sitting position, horizontal - for working standing. The effect of vibration on a person becomes dangerous when the frequency of vibrations of the workplace approaches the frequency of natural vibrations of the organs of the human body: 4-6 Hz - vibrations of the head relative to the body in a standing position, 20-30 Hz - in a sitting position; 4-8 Hz - abdominal cavity; 6-9 Hz - majority internal organs; 0.7 Hz - "rolling" causes motion sickness.

The time characteristics differ:

Constant vibration, for which the controlled parameter changes by no more than 2 times (by 6 dB) during the action;

Unstable vibration, for which these parameters during the observation time change by more than 2 times (by 6 dB).

Under the action of vibration on a person, the vibration velocity (vibration acceleration), frequency range and time of exposure to vibration are estimated. The frequency range of perceived vibrations is from 1 to 1000Hz. Vibrations with a frequency below 20 Hz are perceived by the body only as vibrations, and with a frequency above 20 Hz - simultaneously as vibration and noise.

The effect of vibration on humans

Vibration is one of the factors with significant biological activity. The nature, depth and direction of functional shifts from various systems of the body are determined primarily by the levels, spectral composition and duration of vibration exposure. In the subjective perception of vibration and objective physiological reactions, an important role belongs to the biomechanical properties of the human body as a complex oscillatory system.

The degree of propagation of vibrations throughout the body depends on their frequency and amplitude, the area of ​​the body parts in contact with the vibrating object, the place of application and the direction of the axis of the vibration effect, the damping properties of tissues, the phenomenon of resonance and other conditions. At low frequencies, vibration spreads through the body with very little damping, covering the entire body and head with an oscillatory motion.

Resonance of the human body in biodynamics is defined as a phenomenon in which anatomical structures, organs and systems, under the influence of external vibrational forces applied to the body, receive oscillations of greater amplitude. The resonance of the body, along with its mass, is influenced by such factors as the size, posture and degree of tension of the skeletal muscles of a person, etc.

The resonance area for the head in a sitting position with vertical vibrations is located in the zone between 20 and 30 Hz, with horizontal vibrations - 1.5-2 Hz. The resonance is of particular importance in relation to the organ of vision. The frequency range of visual disturbances lies between 60 and 90 Hz, which corresponds to the resonance of the eyeballs. For thoracoabdominal organs, the resonant frequencies are 3-3.5 Hz. For the whole body in a sitting position, the resonance is determined at frequencies of 4-6 Hz.

In the formation of the body's reactions to vibration load, an important role is played by analyzers: skin, vestibular, motor, for which vibration is an adequate stimulus.

The long-term influence of vibration, combined with a complex of unfavorable production factors, can lead to persistent pathological disorders in the body of workers, the development of vibration disease.

With intense vibration exposure, direct mechanical trauma is not excluded, primarily of the musculoskeletal system: muscles, bones, joints and ligaments.

Clinically, in the development of vibration disease, there are 3 degrees of its development: I degree - initial manifestations, II degree - moderately pronounced manifestations, III degree - pronounced manifestations.

One of the main symptoms of this disease is vascular disorders. Most often, they consist in a violation of peripheral circulation, a change in the tone of capillaries, a violation of general hemodynamics. Patients complain of sudden attacks of whitening of the fingers, which often appear when washing hands cold water or with general cooling of the body.

With the indirect (visual) impact of vibration on a person, there is a psychological effect. For example, oscillating objects (chandeliers, banners, ventilation ducts) suspended from various structures cause unpleasant sensations.

Vibration has a destructive effect on buildings and structures, disrupts the readings of measuring and control devices, reduces the reliability of machines and devices, in some cases causes product defects, etc. Sanitary standards require vibration parameters to be reduced to acceptable values.

Hygienic regulation of vibration acting on a person serves to ensure vibration-safe working conditions. Due to the complexity of assessing the effect of vibration on the systems of the human body and the lack of uniform standardized parameters of vibration exposure, the basis for hygienic regulation vibrations are the objective physiological reactions of a person to vibration of a certain intensity, as well as subjective assessments of the adverse effects of vibration on workers of various professions. With the current level of technology development, it is not always possible to reduce vibration to an absolutely harmless level. Therefore, when standardizing, it is assumed that work is possible not in the best, but in acceptable conditions, i.e. when the harmful effects of vibration are not manifested or manifested insignificantly, without leading to occupational diseases.

The assessment of the degree of harmfulness of vibration of hand-held machines is made according to the spectrum of vibration velocity relative to the threshold value equal to 5 H 10 -8 m / s. The weight of vibrating equipment or its parts, held by hands, should not exceed 10 kg, and the pressure force - 20 kg.

General vibration is normalized taking into account the properties of the source of its origin. The highest requirements are imposed on the regulation of technological vibrations in rooms for mental ore. The hygienic vibration standards are established for a working day of 8 hours.

Vibration protection

Vibration safe working conditions are those under which industrial vibration does not have adverse effects on the worker, in extreme manifestations leading to an occupational disease. The creation of such working conditions is achieved by rationing the parameters of vibrations, organizing work, reducing vibrations at the source of occurrence and along the paths of their propagation, using personal protective equipment.

Reducing vibration of machines can be achieved by reducing vibration activity and internal vibration protection of the source. The reason for low-frequency vibrations of pumps, compressors, electric motors is the imbalance of the rotating elements. The action of unbalanced dynamic forces is aggravated by poor fastening of parts, their wear during operation. Elimination of the imbalance of the rotating masses is achieved by balancing.

To attenuate vibrations, it is important to eliminate resonance modes of operation, i.e. a change in the natural frequencies of the unit and its individual units and parts from the frequency of the driving force. Resonant modes during the operation of technological equipment are eliminated by changing the mass and stiffness system or by setting a different operating mode in frequency (implemented at the equipment design stage). The rigidity of the system is increased by the introduction of stiffeners, for example for thin-walled body elements.

The second method of internal vibration protection is vibration damping, i.e. transformation of the energy of mechanical vibrations of the system into thermal energy. Reducing vibrations in the system is achieved by using construction materials with increased damping properties (high internal friction); applying viscoelastic materials to vibrating surfaces; the use of surface friction (for example, in two-layer composite materials), the conversion of mechanical energy into the energy of an electromagnetic field. Magnesium alloys and manganese-copper alloys, as well as certain grades of cast iron and steel, have increased damping properties. In some cases, plastics, rubber, polyurethane with high damping properties are used as construction materials.

When the use of polymeric materials as structural materials is not possible, vibration damping coatings are used to reduce vibrations: hard - from multilayer and single-layer materials and soft - sheet and mastic. Metal coatings based on aluminum, copper, lead can be used as rigid ones. Lubricants dampen vibrations well.

Reducing vibration along the path of its propagation is achieved by vibration isolation and vibration damping.

Vibration isolation (in the proper sense of this term) is to reduce the transmission of vibration from a source to a protected object (a person or other unit) by introducing an additional elastic connection. For vibration isolation of stationary machines with a vertical exciting force, vibration isolators such as elastic pads or springs are used. Under unfavorable operating conditions (high temperatures, the presence of oils, acid and alkali vapors) and a low excitation frequency (30 Hz), it is recommended to install the equipment on spring (rubber) gaskets. In practice, combined spring-rubber vibration isolators are often used. When calculating rubber gaskets, their thickness and area are determined, the absence of shear deformations in the horizontal plane and resonance phenomena in the gasket material is checked. Calculation of a spring vibration isolator consists in determining the diameter and material of the spring wire, the number of turns and the number of springs.

Vibration damping in the system is achieved using dynamic vibration dampers using the effects of inertia of viscous, dry friction, etc. Vibration dampers with dry friction, pendulum inertial, spring inertial, etc. are widely used. The use of vibration dampers in systems of dynamic damping of elements with their own power sources and installation of equipment on a vibration foundation expands the capabilities of vibration dampers.

A radical solution to the problem of reducing vibrations can be achieved by automating production and introducing remote control of units and sections, as well as by modifying technological processes (for example, pressing on hydraulic presses instead of stamping on hammers, rolling instead of impact straightening).

It is necessary to strive for the optimal arrangement of equipment on the floor in terms of vibration protection; vibrating equipment must be moved from the middle of the span to the supports. If it is impossible to protect personnel with technical measures, "floating" floors are used in the control room, for example, in compressor or pumping stations.

Individual protection means

When working with manual mechanized electric and pneumatic tools, vibration arms and personal protective equipment are used: double-layer gloves (inner cotton, outer rubber), vibration-damping shoes, anti-vibration belts, rubber mats. Considering the adverse effect of cold on the development of vibration sickness, workers are provided with warm gloves when working in winter. Ensuring a rational regime of work and rest.

Physiotherapy procedures:

Dry hand baths;

Massage and self-massage;

Industrial gymnastics;

Ultraviolet irradiation.

To effectively protect workers from noise and vibration, it is necessary to implement complex engineering, technological, organizational and medical measures. This should include the reduction of noise and vibration at the source of their formation, isolation of noise and vibration sources using sound and vibration protection and sound and vibration absorption, the introduction of architectural and planning solutions with the rational placement of technological equipment, machines and mechanisms, the use of personal protective equipment. preventive health measures.
Reducing noise and vibration at their sources is the main and most rational method of protecting workers. This should be taken into account at the design stage, as well as during the operation of technological equipment.
As a rule, to reduce noise, the source is enclosed in an insulated room or the noise level generated by its own sources (technological equipment) is reduced.
To reduce the noise emitted into the insulated room, they improve the sound insulation of ceilings, walls, doors and windows. For example, under the action of low- and medium-frequency noise, the sound insulation of windows can be improved by installing air gaps (up to 100-150 mm thick) between the sashes.
To reduce noise in a room with its own sources, work places are designed to be isolated from the noisiest equipment. For this purpose, the equipment is placed in boxes, provides for the installation of soundproof enclosures above it, and screens, baffles and sound-absorbing partitions are placed on the path of propagation of sound waves. Separate low-noise rooms from rooms with intense sources of noise. For example, it is not allowed to locate laboratories and design offices in the immediate vicinity of gas turbine plants.
Sound insulation in industrial buildings. Sound insulation is understood as the creation of special construction devices - barriers - walls, partitions, casings, ceilings, etc., preventing the propagation of noise. Most often, concrete, brick and ceramic blocks are used for the manufacture of soundproof structures.
To protect the operating personnel from noise, observation and remote control cabins are arranged. Cabin structures must provide the required sound insulation. They are made of lightweight materials, well sealed, and from the inside they are treated with sound-absorbing materials (Figure 11.3).
A simple and inexpensive way to reduce noise from the noisiest units is to install soundproof enclosures above them. The use of housings makes it possible to reduce noise in the workplace to almost any required value. The casings can be removable or collapsible, have viewing windows, openings for entering communications (Fig, 11.4). Sound insulation is improved by applying a layer of sound-absorbing material to the inner surface of the casing walls. Soundproof enclosures are best placed on the floor on a

Rice. 11.3. Soundproof cabins:
1 - ventilation muffler; 2 - exhaust fan; 3 - sheet of steel or aluminum alloy; 4 - plexiglass; 5 - rubber gasket; b - a shell made of a perforated air floor; 7 - sound absorbing material [†]
A

Rice. 11.4. Sound absorbing casing:

rubber gaskets, avoiding contact of the casing elements with the unit.
Sound absorption in industrial premises. To reduce noise in industrial premises, sound absorption methods are used along with sound insulation. When sound waves hit sound-absorbing materials and structures, a significant part of the sound energy is absorbed and converted into other types of energy, mainly heat. Ultra-thin basalt fiber, fiberglass, mineral wool, porous vinyl chloride, acoustic plaster and felt are used as sound-absorbing materials. Sound-absorbing structures include sound-absorbing linings, piece absorbers, chamber silencers. It is advisable to make sound-absorbing facings and install piece absorbers only in the presence of a large number of noise sources high efficiency in production facilities.
Piece sound absorbers are volumetric structures made in the form of prisms, cubes, balls and other figures and suspended indoors. They are made from perforated sheets of metal, foil, plastics and plywood, and from the inside they are pasted over with a cloth or filled with sound-absorbing material. The greatest acoustic efficiency of piece absorbers is achieved when they are placed in the immediate vicinity of a noise source or in places where sound energy is concentrated (Fig. 1] 5).
Sound absorbing facings reduce noise by 6-8 dB in total in the reflected sound area, making the noise less annoying. For their manufacture, mineral wool silane plates are used. In rooms with a large area, honeycomb ceiling structures are arranged. The honeycomb material is silane plates and gypsum.
Acoustic screens are used to protect working people from direct exposure to noise. They are made

solid solid metal or plastic sheets or shields. The side facing the noise source is treated with a 50 - 60 mm thick layer of sound absorber. The linear dimensions of the screen should be 2 - 3 times larger than the dimensions of the noise source. Thanks to the installation of acoustic screens, noise in workplaces is reduced at medium frequencies by up to 10 dB, at high frequencies by up to 15 dB. With sound-absorbing linings, the acoustic performance of the screens increases.
Reducing the noise of ventilation and gas-dynamic installations is achieved mainly by soundproofing the source or by using mufflers that are installed on air ducts, suction ducts, exhaust and air bypass lines.
Vibration protection methods. The main methods for reducing vibration are vibration isolation, vibration absorption and vibration damping.
To create vibration isolation, shaking equipment is installed on vibration isolators, which attenuate the vibration of the machine relative to the supporting structure. As vibration isolators, gaskets made of elastic materials, spring, rubber-metal and other shock absorbers are used. Elastic gaskets (rubber and cork) are used to eliminate high-frequency vibrations. The disadvantage of rubber vibration isolators is their fragility - they serve no more than 15 years.
Steel vibration isolators effectively reduce low frequency vibration, they are more durable and more reliable than rubber ones.
With the help of vibration absorption, they reduce vibrations that propagate along the thin-walled metal structures of machines and air ducts. For this purpose, vibration-absorbing (vibration-damping) coatings made of materials with high internal friction are applied to the surface of thin-walled structures, which makes it possible to increase the loss of vibrational energy in the system due to its transition to thermal energy. Vibration-absorbing coatings are made of rubber, plastic, asbokarpsh or felt impregnated with bitumen. The thickness of the vibration-absorbing coating should be 2 - 3 times greater than the thickness of the structure to be coated.
With the help of vibration damping, mechanical vibrations of structures are weakened. This is done by introducing additional stiffness elements into the oscillatory system. It is also possible to introduce an additional oscillatory system that attenuates the oscillation frequency of the main system. In domestic practice, low-frequency vibration dampers are used for this purpose. To measure noise and vibration, sound level meters (VShM-201), noise and vibration meters (VShV-003-M2) and sound level meters-vibrometers (SHVD 001 and ShVI) are used.

Noises and vibrations, as well as electromagnetic fields and radiation, ionizing radiation and the effects of radionuclides, refer to the energy pollution of the technosphere. Both noise and vibration have an adverse effect on the human body and general well-being, but it is manifested differently... Noises mainly affect the hearing organs, causing hearing loss, and can also cause pathological changes in the cardiovascular system with prolonged exposure, weaken the response and attention of a person.

Noise- this is a combination of sounds of different frequency and intensity adversely affecting a person, randomly changing in time.

Vibrations- these are mechanical vibrations of elastic bodies or vibrational movements of mechanical systems transmitted to the human body or its individual parts.

Vibration mainly affects the internal organs of a person, causing vibration sickness. The main parameters of sound vibrations are sound pressure, sound intensity, frequency, sound waveform. The smallest value of sound pressure perceived by a person at a frequency of 1 kHz is 2 · 10 -5 Pa, called the threshold value.

The smallest value at which pain occurs is 20 Pa (120 dB in level). For most people, the pain threshold is 140 dB.

The most unfavorable for a person is noise lying in the region of average audible frequencies in the range of 1000 - 4000 Hz. The adverse effects of noise depend on the acoustic level (sound pressure level or sound intensity), frequency range, and uniformity of exposure during working hours.

Sound pressure Is the difference between the instantaneous pressure value at a given point of the medium when sound waves pass through it and atmospheric pressure in the absence of sound waves.

The sound pressure level can be determined using the formula:

where is the root-mean-square value of the sound pressure at the point of measurement, Pa;

- zero (threshold) value, Pa.

Noise fluctuations have the property of accumulation in the body (cumulativeness).

The harmfulness of noise as a factor in the working environment leads to the need to limit its level. To prevent and reduce the harmful effects of noise, hygiene standards must be observed.

These standards are based on the limitations of the sound pressure level within the octave bands of the entire noise spectrum, taking into account the nature of the noise and features labor activity.

The frequency range from 16 Hz to 20 kHz is called audible. Frequency range below 16 Hz - infrasonic, above 20 kHz - ultrasonic.

Despite the fact that both infrasounds and ultrasounds are not audible, their levels are also normalized, because have an adverse effect on humans.

Sources of noise in the urban environment are vehicles and industrial equipment, infrasound - technological equipment of impact action, rail transport and pneumatic tools, ultrasound - rocket engines and wind-blown water surfaces and construction sites.

The main parameters of vibration are: frequency and amplitude of vibration that cause vibrations of the human body when vibration propagates through the tissues of the body, vibration velocity and vibration acceleration.

Vibration is general and local. General subdivided into transport, technological, transport and technological. Sanitary standards establish the maximum permissible vibration values.

Personal protective equipment is headphones, earplugs, etc.

The most effective are means that reduce the levels of noise and vibration at the source itself, but this is not always achievable.

Noise and its effect on the body. It was found that the human hearing organ perceives the difference in sound pressure change in the form of a multiplicity of this change, therefore, to measure the noise intensity, a logarithmic scale in decibels is used relative to the hearing threshold (minimum sound pressure perceived by the hearing organ) of a person with normal hearing. This value, equal to 2 · 10 -5 Newton per 1 m 2, is taken as 1 decibel (dB).

When the sound intensity increases, the pressure generated by the sound wave on the eardrum at a certain level can cause pain. This sound intensity is called the pain threshold and is within 130 dB.

In production conditions, as a rule, there are noises of varying intensity and spectrum, which are created as a result of the operation of various mechanisms, units and other devices. They are formed due to rapid rotational movements, sliding (friction), single or repeated shocks, vibration of tools and individual machine parts, turbulence of strong air or gas streams, etc. Noise has different frequencies in its composition, and yet each noise can be characterized the predominance of certain frequencies. It is conventionally accepted to divide the entire spectrum of noise into:

Low-frequency - with an oscillation frequency of up to 350 Hz,

Medium frequency - from 350 to 800 Hz

And high-frequency - over 800 Hz.

Low-frequency noise includes noise from low-speed non-impact units, noise penetrating through soundproof barriers (walls, ceilings, casings), etc .; medium-frequency noise includes the noise of most machines, units, machine tools and other moving devices of non-impact action; high-frequency ones include hissing, whistling, ringing noises characteristic of machines and units operating at high speeds, shock action that create strong flows of air or gases, etc.

Occupational noise of varying intensity and spectrum (frequency), long-term exposure to workers, can eventually lead to a decrease in hearing acuity in the latter, and sometimes to the development of occupational deafness. This adverse effect of noise is associated with prolonged and excessive irritation of the nerve endings of the auditory nerve in the inner ear, as a result of which overwork occurs in them, and then partial destruction. Studies have found that the higher the frequency composition of the noises, the more intense and longer they are, the faster and stronger they have an adverse effect on the hearing organ.

In addition to local action- on the organ of hearing, noise also has a general effect on the body of workers. Noise is an external stimulus that is perceived and analyzed by the cerebral cortex, as a result of which, with intense and long-acting noise, an overstrain of the central nervous system occurs, spreading not only to specific auditory centers, but also to other parts of the brain. As a result, the coordinating activity of the central nervous system is disrupted, which, in turn, leads to a disorder in the functions of internal organs and systems. For example, workers who have been exposed to intense noise for a long time, especially high-frequency noise, complain of headaches, dizziness, tinnitus, and medical examinations reveal peptic ulcer, hypertension, gastritis and other chronic diseases.

The effect of vibration on the body. The perception of vibration depends on the frequency of vibrations, their strength and range - amplitude. Vibration frequency, like sound frequency, is measured in hertz, energy - in kilogram meters, and vibration amplitude - in millimeters. In recent years, it has been established that vibration, like noise, acts on the human body energetically, therefore, it began to be characterized by a spectrum in terms of vibrational speed, measured in centimeters per second or. like noise, in decibels; the threshold value of vibration is conventionally taken as a speed of 5 · 10 -6 cm / sec. Vibration is perceived (felt) only when it comes into direct contact with a vibrating body or through other solid bodies in contact with it. When in contact with a source of vibrations that generates (emitting) sounds of the lowest frequencies (bass), along with the sound, shock is also perceived, that is, vibration.

Depending on which parts of the human body are subject to mechanical vibrations, local and general vibrations are distinguished. With local vibration, only that part of the body that is in direct contact with the vibrating surface, most often the hands, is subjected to shock (when working with hand-held vibrating tools or when holding a vibrating object, machine part, etc.). Sometimes local vibration is transmitted to parts of the body that are articulated with the directly vibrated joints. However, the amplitude of vibrations of these parts of the body is usually lower, since as the vibrations are transmitted through the tissues, and so. softer, they gradually fade. General vibration spreads to the whole body and occurs, as a rule, from the vibration of the surface on which the worker is located (floor, seat, vibration platform, etc.).

The vibrations transmitted from the vibrating surface to the human body irritate numerous nerve endings in the walls of blood vessels, muscle and other tissues. Response impulses lead to disturbances in the normal functional state of some internal organs and systems, and primarily peripheral nerves and blood vessels, causing them to contract. The nerve endings themselves, especially the skin ones, also undergo changes - they become less susceptible to irritation. All this manifests itself in the form of causeless pain in the hands, especially at night, numbness, a feeling of "creeping", sudden whitening of the fingers, a decrease in all types of skin sensitivity (pain, temperature, tactile). This whole complex of symptoms characteristic of vibration exposure is called vibration disease. Patients with vibration sickness usually complain of muscle weakness and fatigue. In addition to this, in women from exposure to vibration, violations of the functional state of the genital area often appear.

The development of vibration disease, etc. other unfavorable phenomena depends mainly on the spectral composition of vibration: the higher the vibration frequency and the greater the amplitude and speed of vibrations, the greater the danger of vibration in relation to the timing and severity of vibration disease.

Cooling of the body, mainly those parts of it that are prone to vibration, muscle tension, especially static, noise, and others, contribute to the development of vibration disease.

Measures to combat noise and vibration. First of all, it is necessary to pay attention to the technological process and equipment, if possible, replace operations accompanied by noise or vibration with others. In some cases, it is possible to replace the forging of metal by stamping, riveting and embossing - by pressing or electric welding, emery cleaning of metal - by fire, sawing with circular saws - by cutting with special scissors, etc. It is necessary to ensure that such a replacement does not create any additional harm which can have a more adverse effect on workers than noise and vibration.

Elimination or reduction of noise and vibration from rotating or moving components and assemblies is achieved, first of all, by precise fitting of all parts and debugging of their work (reduction to a minimum of tolerances between connecting parts, elimination of distortions, balancing, timely lubrication, etc.). Springs or damping material (rubber, felt, cork, soft plastics, etc.) should be placed under rotating or vibrating machines or individual units (between colliding parts).

It is not recommended to place rotating machine parts (wheels, gears, shafts, etc.) on one side of the machine: this complicates balancing and leads to vibration. Vibrating large surfaces that create noise (rattling), such as casings, covers, covers, walls of boilers and tanks when riveting or stripping, etc., should be more tightly connected to fixed parts (bases), laid on shock-absorbing pads or covered with similar material on top.

To prevent turbulence of air or gas flows that create high-frequency noise, it is necessary to carefully mount gas and air communications and devices, especially those under high pressure, avoiding roughness of internal surfaces, protruding parts, sharp turns, leaks, etc. To release compressed air or gas should be used not simple valves, but special valves.

An important role in the fight against noise and vibration is played by architectural and construction and planning solutions in the design and construction of industrial buildings. First of all, it is necessary to remove the most noisy and vibrating equipment outside the production premises where the workers are located; if this equipment requires constant or frequent periodic monitoring, soundproof booths or rooms for service personnel are equipped at the site of its placement.

Rooms with noisy and vibrating equipment should be isolated as much as possible from other work areas. Similarly, it is advisable to isolate rooms or areas with noise of different intensity and spectrum. Walls and ceilings in noisy rooms are covered with sound-absorbing materials, acoustic plaster, soft draperies, perforated panels with slag wool lining, etc.

Powerful machines and other rotary or impact equipment are installed in the ground floor on a special foundation completely separated from the main foundation of the building, as well as from the floor and supporting structures. Such equipment of lower power is installed on the supporting structures of the building with gaskets made of shock-absorbing materials or on consoles attached to the main walls. Equipment that generates noise is covered or enclosed in insulated cabins with sound-absorbing covers. Gas or air communications are also soundproofed through which noise can propagate (from compressors, pneumatic drives, fans, etc.).

As personal protective equipment when working in noisy rooms, various anti-noise (anti-phonics) are used. They are made either in the form of inserts made of soft sound-absorbing materials inserted into the external auditory canal, or in the form of headphones that are worn on the auricle.

When working in conditions of general vibration, a special vibration-damping (shock-absorbing) platform is placed under the worker's feet. When exposed to local vibration (more often on the hands), handles and others vibrate; vibrating parts of machines and tools (for example, a pneumatic hammer) in contact with the worker's body are covered with rubber. or other soft material. Gloves also play a vibration-damping role. Vibration control measures are provided not only when working directly with vibrating tools, machines or other equipment, but also when in contact with parts and tools that are exposed to vibration from the main source.

It is necessary to organize the work process in such a way that operations accompanied by noise or vibration alternate with other work without these factors. If it is impossible to organize such an alternation, it is necessary to provide for periodic short breaks in work with the shutdown of noisy or vibrating equipment or the removal of workers to another room. Avoid significant physical activity, especially static stress, as well as cooling of the hands and the whole body; during breaks, be sure to do physical exercises (physical training pauses).

When hiring a job associated with possible exposure to noise or vibration, mandatory preliminary medical examinations are carried out, and in the process of work - periodic medical examinations once a year.

Ultrasound and its effect on the body, preventive measures. In industrial conditions, to obtain ultrasound, installations are used, consisting of high-frequency alternating current generators and a magnetic transducer.

Ultrasound is capable of propagating in all media: gaseous, including air, liquid and solid. When ultrasound is used for industrial purposes, the vibrations created by its source are most often transmitted through a liquid medium (when cleaning, degreasing, etc.) or through a solid medium (when drilling, cutting, grinding, etc.). However, in both cases, some part of the energy generated. a source of ultrasound, passes into the air, in which ultrasonic vibrations also occur.

Ultrasound is evaluated according to its two main parameters:

Oscillation frequency

And the sound pressure level.

Oscillation frequency, like noise and vibration, is measured in hertz or kilohertz (1 khz equals 1000 Hz). The intensity of ultrasound propagated in air and gas, as well as noise, is measured in decibels.

The intensity of ultrasound propagated through a liquid or solid medium is usually expressed in units of the power emitted by a magnetostrictive transducer per unit of irradiated surface - watts per square centimeter (W / cm 2).

Ultrasonic vibrations directly at the source of their formation propagate directionally, but already at a short distance from the source (25 - 50 cm), these vibrations transform into concentric waves, filling the entire working room with ultrasound and high-frequency noise.

When working on ultrasonic installations of significant capacities, workers complain of headaches, which, as a rule, disappear at the end of the work; unpleasant noise and squeak in the ears (sometimes to painful sensations), which persist even after the end of work; rapid fatigue, sleep disturbance (more often daytime sleepiness), sometimes weakening of vision and a feeling of pressure on the eyeball, poor appetite, dry mouth and stiffness of the tongue, abdominal pain, etc. When examining these workers, they reveal some physiological changes during work , expressed in a slight increase in body temperature (by 0.5 - 1.0 o C) and skin (by 1.0 - 3.0 o C), a decrease in heart rate (by 5 - 10 beats per minute), a decrease in blood pressure - hypotension (maximum pressure up to 85 - 80 mm Hg., and minimum - up to 55 - 50 mm Hg. Art.), slightly slowed down reflexes, etc. Workers with long experience sometimes have individual deviations from the side of health, that is clinical manifestations: emaciation (weight loss up to 5-8 kg), persistent appetite disorder (aversion to food up to nausea or insatiable hunger), impaired thermoregulation, dullness of the skin sensitivity of the hands, decreased hearing and vision, dysfunction of the endocrine glands, etc. All these manifestations should be regarded as a result of the combined action of ultrasound and the accompanying high-frequency noise. In this case, contact irradiation with ultrasound causes faster and more pronounced changes in the body of workers than exposure through the air. With an increase in the experience of working with ultrasound, the phenomena of its adverse effects on the body also increase. Individuals who have worked in these conditions for up to 2 - 3 years usually rarely reveal any pathological changes even with intense doses of ultrasound exposure. In addition, the degree of adverse effects of ultrasound depends on its intensity and duration of exposure, both one-time and total per work shift.

Prevention of the adverse effect of ultrasound and the accompanying noise on the body of workers should first of all be reduced to a minimum of the intensity of ultrasonic radiation and the duration of action. Therefore, when choosing an ultrasound source for carrying out a particular technological operation, one should not use powers that exceed those required for their implementation; they need to be turned on only for the period of time that is required to perform this operation.

Ultrasound installations and their individual units (high-frequency current generators, magnetostrictive converters, baths) should be soundproofed as much as possible by enclosing them in shelters, isolation in separate cabins or rooms, covering with soundproof material, etc. If complete sound insulation is impossible, partial insulation is used, and also sound absorbing screens and coverings.

The most common personal protective equipment when working with ultrasound are ear muffs and gloves. It is advisable to have the latter two-layer: rubber on the outside, and cotton or woolen on the inside, they absorb vibrations better and are waterproof.

If the initial signs of an adverse effect of ultrasound on the body of workers are detected, it is necessary to temporarily stop working in contact with ultrasound (another vacation, transfer to another job), which leads to a rapid disappearance of the symptoms of exposure.

All newcomers to work with ultrasound are subject to mandatory preliminary medical examination, and in the future - periodic medical examinations at least once a year.

MOSCOW HUMANITARIAN AND ECONOMIC INSTITUTE

Tver branch

FOUNDATION LECTURE

by academic discipline

Life safety

Noise and vibration protection

L. V. Pyanova

Tver 2014

The fund lecture "Protection against noise and vibration" was discussed and recommended for publication at a meeting of the Department of General Humanitarian Disciplines of the TF MGEI. Minutes No. 2 dated October 15, 2014.

Reviewers:

candidate of chemical sciences, associate professor

Mukhometzyanov A.G.

Pyanova L.V. Protection against noise and vibration: Stock lecture. - Tver: Publishing house of the TF MGEI, 2014.117 p.

The fund lecture "Protection against noise and vibration" is intended for full-time and part-time students of the direction 030300.62 "Psychology", 080100.62 "Economics", 080200.62 "Management", 030900.62 "Jurisprudence" tovalidation (degree) of a bachelor's degree graduate from the Tver branch of the Moscow State Power Engineering Institute and may be useful in independent study of the problems of human life and environment safety, labor protection, and environmental safety.

L. V. Pyanova

Moscow Institute of Humanities and Economics

2014

Introduction ................................................. .................................................. ....................4

1. Physical characteristics of noise ............................................. ...........................nine

2. The effect of noise and vibration on the human body ......................................... ...13

3. Normalization of noise and vibration ............................................ ............................19

4. Elimination or reduction of noise in the sources of its formation ................ 21

5. General methods of dealing with vibration ........................................... ..................... 25

6. Means of collective and individual protection against noise and vibration ..... 26

7. Instruments for measuring noise and vibration .......................................... ............ 34

Conclusion................................................. .................................................. ............ 36

Introduction

With the help of the auditory analyzer, a person is guided by the sound signals of the environment, forms the appropriate behavioral reactions, for example, defensive or food-processing. The ability of a person to perceive spoken and vocal speech, musical works makes the auditory analyzer a necessary component of means of communication, cognition, and adaptation.

Sounds are an adequate stimulus for the auditory analyzer, i.e. vibrational motion of particles of elastic bodies, propagating in the form of waves in a variety of media, including air, and perceived by the ear. Sound wave vibrations (sound waves) are characterized by frequency and amplitude. The frequency of the sound waves determines the pitch. A person distinguishes sound waves with a frequency of 20 to 20,000 Hz. Sounds with a frequency below 20 Hz (infrasounds) and above 20,000 Hz (20 kHz) (ultrasounds) are not felt by a person. Sound waves that have sinusoidal or harmonic vibrations are called tone. Sound consisting of unrelated frequencies is called noise. At high frequencysound waves, the tone is high, with low - low. The second characteristic of sound that the auditory sensory system distinguishes is its strength, which depends on the amplitude of the sound waves. The strength of the sound or its intensity perceived human as loudness. The sensation of loudness increases with sound amplification and also depends on the frequency of sound vibrations, i.e. the loudness of the sound is determined by the interaction of the intensity (strength) and the pitch (frequency) of the sound. The unit for measuring the loudness of a sound is bel, in practice the decibel (dB) is usually used, i.e. 0.1 is white. A person also distinguishes sounds by timbre ("color"). The timbre of the audio signal depends on the spectrum, i.e. from the composition of additional frequencies (overtones) that accompany the main tone (frequency). By timbre, you can distinguish sounds of the same pitch and volume, which is the basis for recognizing people by voice.

The sensitivity of the auditory analyzer is determined by the minimum sound intensity sufficient to cause auditory sensation... In the range of sound vibrations from 1000 to 3000 per second, which corresponds to human speech, the ear has the greatest sensitivity. This set of frequencies is called the speech zone. In this area, sounds with a pressure of less than 0.001 bar are perceived (1 bar is approximately one millionth of normal atmospheric pressure). Based on this, in transmitting devices, in order to provide an adequate understanding of speech, speech information must be transmitted in the speech frequency range.

Departments of the auditory analyzer. The peripheral part of the auditory analyzer, which converts the energy of sound waves into the energy of nervous excitement, is the receptor hair cells of the organ of Corti (organ of Corti) located in the cochlea. Auditory receptors (phonoreceptors) belong to mechanoreceptors, are secondary and are represented by internal and external hair cells. In humans, there are approximately 3,500 inner and 20,000 outer hair cells, which are located on the basal membrane inside the middle canal of the inner ear. The internal (sound-receiving apparatus), as well as the middle (sound-transmitting apparatus) and the outer ear (sound-collecting apparatus) are combined into the concept of an organ of hearing.

The external ear, due to the auricle, provides the capture of sounds, their concentration in the direction of the external auditory canal and the intensification of the intensity of sounds. In addition, the structures of the outer ear perform a protective function, protecting the eardrum from mechanical and temperature effects of the external environment.

The middle ear (sound-conducting section) is represented by the tympanic cavity, where three auditory ossicles are located: the malleus, the incus and the stapes. The middle ear is separated from the external auditory canal by the tympanic

membrane. The handle of the malleus is woven into the tympanic membrane, its other end is articulated with the incus, which in turn is articulated with the stapes. The stripe adjoins the membrane of the oval window. The area of ​​the tympanic membrane (70 mm2) is much larger than the area of ​​the oval window (3.2 mm2), due to which the pressure of sound waves on the membrane of the oval window is increased by about 25 times. Bone linkage reduces the amplitude of sound wavesapproximately 2 times - therefore, the same amplification of sound waves occurs on the oval window. Thus, the middle ear amplifies the sound by about 60-70 times. If we take into account the reinforcing effect of the outer ear, then this value increases 180-200 times. The middle ear has a special defense mechanism, represented by two muscles - the muscle that pulls the eardrum and the muscle that fixes the stapes. The degree of contraction of these muscles depends on the strength of the sound vibrations. With strong sound vibrations, the muscles limit the amplitudevibrations of the tympanic membrane and movement of the stapes, thereby protecting the receptor apparatus of the inner ear from excessive excitation and destruction. In case of instantaneous strong stimuli (ringing the bell), this defense mechanism does not have time to be triggered. The contraction of both muscles of the tympanic cavity is carried out by the mechanism of an unconditioned reflex, which is closed at the level of the brainstem.

In the tympanic cavity, a pressure equal to atmospheric pressure is maintained, which is very important for adequate perception of sounds. This function is performed by the Eustachian tube, which connects the middle ear cavity with the pharynx. When swallowing, the tube opens, ventilating the middle ear cavity and equalizing the pressure in it with atmospheric pressure. If the external pressure changes rapidly (rapid rise to altitude), and swallowing does not occur, then the pressure difference between atmospheric air and air in the tympanic cavity leads to tension in the tympanic membrane and the emergence of unpleasant sensations ("ear popping"), a decrease in the perception of sounds.

The inner ear is represented by a cochlea — a helically twisted bony canal with 2.5 curls, which is divided by the main membrane and Reisner's membrane into three narrow parts (ladders). The upper canal (vestibular ladder) starts from the oval window, connects to the lower canal (tympanic ladder) through a helicotreme (hole in the apex) and ends with a round window. Both channels form a single whole and are filled with a perilymph similar in composition to cerebrospinal fluid... Between the upper and lower channels is the middle (middle staircase). It is isolated and filled with endolymph. Inside the middle channel on the main membranethe actual sound-perceiving apparatus is located - the organ of Corti (organ of Corti) with receptor cells, which represents the peripheral part of the auditory analyzer. The main membrane near the oval window is 0.04 mm wide, then towards the apex it gradually expands, reaching 0.5 mm at the helicotre. Above the organ of Corti lies a tectorial (integumentary) membrane of connective tissue origin, one edge of which is fixed, the other is free. The hairs of the outer and inner hair cells are in contact with the tectorial membrane. In this case, the energy of sound waves is transformed into a nerve impulse.

The conductive section of the auditory analyzer is represented by a peripheral bipolar neuron located in the spiral ganglion of the cochlea (first neuron). The fibers of the auditory (or cochlear) nerve, formed by the axons of the spiral ganglion neurons, end on the cells of the nuclei of the cochlear complex medulla oblongata(second neuron). Then, after partial crossing, the fibers go tothe medial geniculate body of the metathalamus, where switching occurs again (third neuron), from here the excitation enters the cortex (fourth neuron). In the medial (internal) geniculate bodies, as well as in the lower tubercles of the quadruple, are the centers of reflex motor reactions arising from the action

sound.

The cortical section of the auditory analyzer is located in the upper part of the temporal lobe of the large brain (superior temporal gyrus, 41st and 42nd fields according to Brodmann). The transverse temporal gyri (Heschl's gyrus) are important for the function of the auditory analyzer.

The auditory sensory system is supplemented by feedback mechanisms that regulate the activity of all levels of the auditory analyzer with the participation of descending pathways. Such pathways start from the cells of the auditory cortex, switching sequentially in the medial geniculate bodies of the metathalamus, the posterior (lower) tubercles of the quadruple, in the nuclei of the cochlear complex. As part of the auditory nerve, centrifugal fibers reach the hair cells of the organ of Corti and tune them to the perception of certain sound signals.

1. Physical characteristics of noise

Noise as a hygienic factor is a combination of sounds of various frequencies and intensities, which are perceived by the human hearing organs and cause unpleasant subjective sensations.

Noise as a physical factor is a wave-like propagating mechanical oscillatory motion of an elastic medium, which is usually of a random nature.

Noise is classified by following signs:

1. by the nature of the spectrum:

- broadband with a continuous spectrum more than one octave wide;

The tonal nature of noise for practical purposes (when monitoring its parameters at workplaces) is established by measuring in one-third octave frequency bands by exceeding the sound pressure level in one band over

neighboring by at least 10 dB.

2. By time characteristics:

Constant, the sound level of which over an 8-hour working day (work shift) changes in time by no more than 5 dB A when measured on the time characteristic of a "slow" sound level meter in accordance with GOST 17187;

Unstable, the sound level of which over an 8-hour working day (work shift) changes in time by more than 5 dB A when measured on the time characteristic of a "slow" sound level meter in accordance with GOST 17187.

Intermittent noise should be classified into:

Fluctuating in time, the sound level of which is continuously changing over time;

Intermittent, the sound level of which changes stepwise (by 5 dB A or more), and the duration of the intervals during which the level remains constant is 1 s or more;

Pulse, consisting of one or more sound signals, each with a duration of less than 1 s, while the sound levels measured in dB AI and dB A, respectively, on the time characteristics of the "impulse" and "slow" sound level meter according to GOST 17187 differ by at least 7 dB.

3. By frequency:

Low frequency;

Mid-frequency;

High frequency.

4. By the nature of occurrence:

Mechanical;

Aerodynamic;

Hydraulic;

Electromagnetic.

TO physical characteristics noise include - speed of propagation; frequency; power; sound pressure (sound pressure);

volume.

Sound propagation speed. Noise travels at a much slower speed than light waves. The speed of sound in air is about 330 m / s, in liquids and solids the speed of noise propagation is higher, it depends on the density and structure of the substance.

For example, the speed of sound in water is 1.4 km / s, and in steel it is 4.9 km / s.

Noise frequency. The main parameter of noise is its frequency (the number of vibrations per second). The unit of measurement for frequency is 1 hertz (Hz), which equals 1 sound wave vibration per second. Human hearing picks up frequency fluctuations from 20 Hz to 20,000 Hz. During the operation of air conditioning systems, the frequency spectrum from 60 to 4000 Hz is usually taken into account. For physical calculations, the audible frequency band is divided into 8 wave groups. In each group, the average frequency is determined: 62 Hz, 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2 kHz, 4 kHz and 8 kHz.

Any noise is decomposed into groups of frequencies, and you can find the distribution of sound energy at different frequencies.

The sound power of an installation is the energy released by the installation in the form of noise per unit of time. It is inconvenient to measure the strength of noise in standard power units, since the spectrum of sound frequencies is very wide, and the power of sounds differs by many orders of magnitude.

For example, the power of noise when air enters a room under low pressure is equal to one hundred billion watt, and when a jet plane takes off, the power of noise reaches 1000 W.

Therefore, the sound power level is measured in logarithmic units - decibels (dB). In decibels, the strength of the noise is expressed in two or three-digit numbers, which is convenient for calculations.

The sound power level in dB is a function of the ratio of the power of sound waves near the noise source to the zero value W0, equal to 10 - 12W.

The power level is calculated using the formula: Lw = 10lg (W / W0)

For example, if the sound power near the source is 10 W, then the level

power will be 130 dB, and if the sound power is 0.001 W, then the power level is 90 dB.

Sound power and power level are independent of the distance to the noise source. They are related only to the parameters and operating mode of the unit, therefore, they are important for the design and comparison of various air conditioning and ventilation systems.

The power level cannot be measured directly, it is determined indirectly by special equipment.

Sound pressure level (Lp) is the perceived intensity of the noise, measured in dB and measured by the formula: Lp = P / P0

Here P is the sound pressure at the measured location, μPa, and P0 = 2 μPa is the reference value.

The sound pressure level depends on external factors: distance from the installation, sound reflection, etc. The simplest form is the dependence of the pressure level on the distance. If the noise power level Lw is known, then the sound pressure level Lp in dB at a distance r (in meters) from the source is calculated as follows: Lp = Lw - logr - 11

For example, the sound power of the refrigeration unit is 78 dB. The sound pressure level at a distance of 10 m from it is: (78 - lg10 - 11) dB = 66 dB.

If the sound pressure level Lp1 is known at a distance r1 from the noise source, then the sound pressure level Lp2 at a distance r2 will be calculated as follows: Lp2 = Lp1 - 20 * log (r2 / r1)

In general, in an open space, the sound pressure level decreases by 6 dB when the distance to the noise source increases by 2 times. In a room, dependence will be more difficult due to the absorption of sound by the floor surface, sound reflection, etc.

The volume of the noise. Human sensitivity to sounds of different frequencies is not the same. It is maximum for sounds with a frequency of about 4 kHz, is stable in the range from 200 to 2000 Hz, and decreases at a frequency of less than 200 Hz.

(low frequency sounds).

The volume of the noise depends on the strength of the sound and its frequency. The loudness of the sound is estimated by comparing it with the loudness of a simple sound signal with a frequency of 1000 Hz. The level of sound intensity with a frequency of 1000 Hz, as loud as the noise being measured, is called the loudness level of that noise.

At a low volume level, a person is less sensitive to sounds of very low and high frequencies. At high sound pressure, the sensation of sound develops into a pain sensation. At a frequency of 1 kHz, the pain threshold corresponds to a pressure of 20 Pa and a sound power of 10 W / m2.

2. The effect of noise and vibration on the human body.

Such problems of modern megacities as noise and vibration are increasing in intensity every year. Why has modern science been so active in recent years to investigate the problem of the influence of noise and vibration on the human body? Why has vibration measurement become a must-have research in many businesses and organizations? Yes, because modern medicine has begun to sound the alarm: the number of occupational diseases- vibration disease and hearing loss arising from prolonged exposure to noise and vibration on an employee of such an enterprise. And the risk groups turned out to be many professions associated just with working in these conditions.

Noise is a complex of sounds that causes an unpleasant sensation or painful reactions. Noise is one of the forms of the physical environment of life. The effect of noise on the body depends on age, auditory sensitivity, duration of action, character. Noise interferes with normal rest, causes diseases of the hearing organs, contributes to an increase in the number of other diseases, and has a depressing effect on the human psyche. Noise is as slow a killer as chemical poisoning. The first ones that have come down to us

complaints about noise can be found in the Roman satirist Juvenal (60-127).

Each person has a number of specialized peripheral formations - sense organs, which provide the perception of external stimuli acting on the body (from the environment). These include the organs of sight, hearing, smell, taste and touch. To lead a full-fledged lifestyle, a person needs all these organs, but external stimuli from his environment can lead to the loss of one of them.

Hearing is the body's ability to perceive and distinguish sound vibrations. The organ of hearing is the ear, it has access to the area of ​​sounds - mechanical vibrations with a frequency of 16-20000 Hz, but the human auditory analyzer has an acoustic reflex of blocking sound in response to an intense sound stimulus, thus, the hearing organ performs two tasks: it supplies the body with information and ensures self-preservation.

The development of technology and industrial production was accompanied by an increase in the level of noise affecting humans. We live in the age of speeds, where it is acceptable to use high-speed machine tools and units in the production (motors, pumps, compressors, turbines, crushers, centrifuges, and other installations with moving parts).

Under industrial conditions, the impact of noise on the body is often combined with other negative effects: toxic substances, temperature changes, vibration, etc.

In recent years, due to the increase in the number of vehicles, the intensity of noise in everyday life has also increased, therefore, as an unfavorable factor, it has acquired a large social significance... The increase in the number and development of transport has led to noise pollution of the environment, in order to somehow stabilize the current situation, many measures are being taken, first of all, these are requirements to limit noise. The new rules should lead to significant changes that will especially affect the part of the population that

is most affected by noise generated by different kinds transport (freight transport, trains, aircraft, etc.).

There are many sources of noise. Different sources generate different noises. These are aerodynamic noises of aircraft, the roar of diesel engines, blows of pneumatic tools, vibrations of all kinds of structures, loud music and much more.

To assess various noises, sound levels are measured using sound level meters in accordance with GOST 17.187-81. Loudness and loudness level are used to assess the physical impact of noise on a person. Hearing threshold changes with frequency, decreases with increasingsound frequency from 16 to 4000 Hz, then increases with increasing frequency up to 20000 Hz. For example, a sound producing a 20dB SPL at 1000Hz will have the same volume as a 50dB sound at 125Hz. Therefore, the sound of the same volume level at different frequencies has a different intensity.

For the characteristic of constant noise, the characteristic is the sound level, measured on the A scale of the sound level meter in dBA.

Noises that are not constant in time are characterized by an equivalent (in energy) sound level in dBA, determined in accordance with GOST 12.1.050-86.

As numerous studies have shown, noise pollution, especially in large cities, is almost always local in nature and this is mainly caused by means of transport - urban, rail and aviation. Already now, on the main highways of large cities, noise levels exceed 90 dB and tend to increase annually, which is the greatest danger to both the environment and humans.

Noise is an unpleasant or undesirable sound or a set of sounds that interfere with the perception of useful signals, disturb the silence, have a harmful or irritating effect on the human body, and reduce its performance.

Noise is a general biological irritant and, under certain conditions, can affect all organs and systems of the whole organism, causing various physiological changes.

Noise acts on the body as a stress factor, causes a change in the sound analyzer, and also, due to the close connection of the auditory system with numerous nerve centers at a very different level, profound changes occur in the central nervous system.

Most dangerous long-term action noise, in which the development of noise sickness is possible - a general disease of the body with a predominant damage to the organ of hearing, central nervous and cardiovascular systems.

The problem of vibration is of particular relevance today. The most favorable conditions for vibration propagation are created using shallow dimple tunnels, the construction of which is economically viable. Metro routes are laid under residential areas, and the experience of operating underground trains shows that vibration penetrates residential buildings within a radius of 40-70 meters from the underground tunnel.

Vibration is called mechanical rhythmic vibrations of elastic bodies. Most often, vibration is understood as unwanted vibrations. Arrhythmic vibrations are called tremors. Vibration propagates due to the transfer of vibration energy from vibrating particles to neighboring particles. This energy at any moment is proportional to the square of the speed of the vibrational motion, therefore, by the magnitude of the latter, one can judge the intensity of vibration, i.e., the flow of vibrational energy. Since the velocities of the oscillatory motion change in time from zero to the maximum, they are estimated using not the instantaneous maximum values, but the rms value over the period of oscillation or measurement. Unlike sound, vibration is perceived by various organs and body particles. So, with low frequency (up to 15 Hz)

vibrations, translational vibration is perceived by the otolith, and rotational - by the vestibular apparatus of the inner ear. Upon contact with a solid vibrating body, the vibration is perceived by the nerve endings of the skin. The strength of the perception of mechanical vibrations depends on the biomechanical reaction of the human body, which is to a certain extent a mechanical vibrational system with its own resonance and resonance of individual organs, which determines the strict frequency dependence of many biological effects vibration. So, in a person in a sitting position, the resonance of the body, which is caused by the influence of vibration and is manifested by unpleasant subjective sensations, occurs at frequencies of 4-6 Hz, in a person in a standing position - at frequencies of 5-12 Hz. A person feels vibration with a frequency from fractions of a hertz to 800 Hz, vibration of a high frequency is perceived like ultrasonic vibrations, causing a feeling of warmth. A person senses oscillatory speeds that differ by 10,000 times. Therefore, by analogy with noise, vibration intensity is often evaluated as the level of vibrational velocity (vibration velocity), determining it in decibels. For the threshold vibrational velocity, the value 5 10 "8 m / s is taken, which corresponds to the threshold sound pressure 2 10 ~ 5 N / m2.

The degree of the adverse effect of vibration depends on its level (or the distance to the source of low-frequency vibrations), time of day, age, type of activity and state of human health.

Vibration that penetrates living quarters as a result of long-term exposure around the clock can have an adverse effect on urban dwellers. Studies carried out in one of the districts of the Federal Republic of Germany have shown that industrial enterprises and transport in a large city are one of the causes of vibration discomfort in apartments. Of the total number of respondents, 42% of residents complained about a slight inconvenience, 15.5% - a tangible inconvenience, 14.4% complained about

irritating effect, and only 27.5% did not feel any inconvenience.

With a short exposure to vibration (1.5 years), functional disorders Central nervous system. In the population group with a longer period of residence (7 years), violations of the cardiovascular system are more often recorded.

The essence of the problem lies in the fact that a constant increased value of vibration leads to rapid fatigue, disruption of the nervous system, poor sleep, and headache. Operating under constant vibration conditions can lead to vibration sickness. Vibration pathology ranks second among occupational diseases.

The scourge of modern production is local vibration. Local vibration mainly causes spasms of the vessels of the hand and forearms, disrupting the supply of blood to the extremities. At the same time, vibrations act on nerve endings, muscle and bone tissues, cause a decrease in skin sensitivity, salt deposition in the joints of the fingers, deforming and reducing the mobility of the joints.

Sources of vibration can be external: vehicles that create high dynamic loads during operation, which cause the propagation of vibration in the ground and building structures of buildings (these vibrations are often also the cause of noise in buildings), subways, heavy trucks, railway trains, trams ; and internal: engineering and sanitary equipment (it can be located in the adjacent rooms of your apartment or office), elevators, pumps, machine tools, transformers, centrifuges.

The problem is that a constant high vibration value leads to fatigue, nervous system disorders, poor sleep, and headaches. Operating under constant vibration conditions can lead to vibration sickness. Vibration pathology ranks second among occupational diseases.

3. Normalization of noise and vibration.

Noise normalization is carried out according to the limiting noise spectrum and sound pressure level. In the first method, the maximum permissible sound pressure levels are normalized in octave frequency bands with geometric mean frequencies of 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 Hz. The combination of the nine permissible sound pressure levels is called the limit spectrum.

The second method of normalizing the total noise level, measured on the A-scale of a sound level meter and called the sound level in dBA, is used for a rough estimate of constant and variable noise, since in this case the noise spectrum is unknown.

In industrial environments, noise is often intermittent. Under these conditions, it is most convenient to use a certain average value, called the equivalent (in energy) sound level Leq and characterizing the average value of the sound energy to dBA. This level is measured by special integrating sound level meters or calculated.

The noise level standards are regulated by the "Sanitary Standards for Acceptable Noise Levels at Workplaces" No. 3223-85, approved by the Ministry of Health, depending on their classification by spectral composition and time characteristics, type of labor activity.

From the point of view of biological effects, the spectral composition and duration of the noise action are essential. Therefore, corrections are introduced to the permissible sound pressure levels, taking into account the spectral composition and temporal structure of the noise. The most unfavorable effects are tonal and impulse noises. Tonal noise is considered to be the noise in which the sound of a certain frequency is heard. Impulsive noise refers to noise perceived as individual shocks and consisting of one or more pulses of sound energy with a duration of each

less than 1 s. Broadband noise is noise in which sound energy is distributed across the entire audio spectrum. Obviously, with an increase in the duration of exposure to noise during the shift, the absolute values ​​of the corrections decrease. At the same time, they are higher for broadband than for tonal or impulse noise. At permanent workplaces, the permissible sound level is 80 dBA.

Methods for hygienic assessment of workplace vibration, standardized parameters and their permissible values ​​are established by Sanitary Standards for Workplace Vibration SN 3044-84.

A hygienic assessment of vibrations affecting a person at a workplace in an industrial environment is carried out by the following methods:

1. frequency (spectral, analysis of the normalized parameter. It is the main method that characterizes the vibration effect on a person;

integral assessment of the frequency of the normalized parameter, used for an approximate assessment;

2. the dose of vibration used to assess vibration taking into account the exposure time.

In frequency analysis, the normalized parameters are the root-mean-square values ​​of vibration velocity V and vibration acceleration a (or their logarithmic levels Lv, Lа), measured in octave or one-third-octave frequency bands (for general narrow-band vibrations, only in one-third octave frequency bands).

In the case of integral estimation by frequency, the normalized parameter is the corrected value of vibration velocity and vibration acceleration and (or their logarithmic levels Lu), measured using corrective filters or calculated by formulas.

In the dose assessment of vibration, the normalized parameter is the energy equivalent corrected value (or its logarithmic level Lueq), determined by the formula.

4. Elimination or reduction of noise in the sources of its formation

Measures to combat noise and vibration can be divided into two main groups: organizational and technical. The main organizational activities are:

1.exclusion of vibroacoustic equipment from the technological scheme;

2. use of equipment with minimal dynamic loads, its correct installation;

3. correct operation of the equipment, its timely inspection and preventive maintenance;

4. placement of noisy equipment in separate rooms, its separation with soundproof partitions;

5. location of noisy workshops away from other production facilities;

6. remote control of vibroacoustic equipment from cabins;

7. use of PPE against noise and vibration;

8. Carrying out sanitary and preventive measures (rational work and rest regimes, professional examinations, etc.) for those working on vibroacoustic equipment.

The main directions of noise control is its attenuation or elimination directly at the source of education.

This is achieved by replacing shock processes and machines with shockless ones, changing the design of units that create noise (for example, using equipment with a hydraulic drive instead of equipment with crank or eccentric drives); replacing the reciprocating movement of parts with a uniform rotational one (for example, replacing stamping in the production of biscuits by pressing between the roller and the conveyor belt); the use of plastics, textolite, rubber and other materials for

manufacturing of equipment parts (for example, replacing metal plate conveyors in filling shops for transporting bottles with plastic coated surfaces of the sides facing the bottles with strips of sound-absorbing materials, for example, polystyrene).

One of the simplest and most economically feasible ways to reduce noise from machines and mechanisms in industrial premises is the use of sound absorption and sound insulation methods.

Sound absorption is based on the property of building materials to dissipate the energy of sound vibrations, converting it into heat. Porous and fibrous materials have the greatest sound-absorbing effect. Sound waves when they meet a porous barrier are partially reflected and partially absorbed. Based on the law of conservation of energy, we have

Where α, β, τ are, respectively, the coefficients of sound absorption, reflection and sound conductivity of the obstacle, which characterize its corresponding properties.

Where Epogl, Eotr, Eprot, Epad - respectively absorbed, reflected, transmitted and incident on the obstacle sound energy.

Sound-absorbing materials are considered to have α> 0.2 (fiberboard plates, fiberglass, mineral wool, polyurethane foam, porous polyvinyl chloride, etc.). Sound-absorbing coatings and facings reduce the overall noise level by no more than 8-10 dB, and in some octave bands of the noise spectrum - up to 12-15 dB.

Sound absorbing coatings and claddings are usually placed on ceilings and walls and are especially effective in rooms with high ceilings and long lengths. To obtain the maximum effect, the area of ​​the lined surface should be at least. 60% of the total area of ​​the room-bounding surfaces. If the area of ​​free surfaces due to light openings is less than indicated, piece (functional) absorbers, suspended above and near noisy equipment, should be additionally used. Piece absorbers are flat curtains and beams or volumetric structures in the form of prisms, balls, etc., filled with sound-absorbing material (fiberglass, etc.).

To prevent the spread of noise, its source is isolated (partially or completely) by means of fences (walls, partitions, ceilings, casings and screens) that reflect sound energy. The soundproofing ability of fences depends on the acoustic properties of materials (the speed of sound in the field), geometrical dimensions, the number of layers of material, mass, elasticity, the quality of the fastening of the fence, the frequency of its natural vibrations and the frequency response of noise.

Acoustic screens are shields lined from the side of the noise source with sound-absorbing material with a thickness of at least 50-60 mm. They should be used to protect the serviced and neighboring units from noise, if sound-absorbing facings do not ensure compliance with hygiene standards. Their purpose is to reduce the intensity of direct sound or to isolate noisy equipment or areas from the rest of the room. The screen is an obstruction behind which an acoustic shadow is formed with a reduced sound pressure level of direct noise. It is most effective against high and medium frequency noise and has little effect on low frequency noise that bends around screens due to diffraction. The linear dimensions of the screen should be at least 2-3 times larger than the linear dimensions of the noise source. It is advisable to use them

for protection from noise sources that create sound pressure levels at the points under consideration, exceeding the permissible by at least 10 dB and not more than 20 dB.

The soundproofing qualities of the fence are determined by the sound conductivity coefficient. For a diffuse sound field, in which all directions of propagation of direct and reflected sound waves are equally probable, the sound insulation value of the fence can be calculated using the formula (in dB): R = 101gl / τ.

Silencers of noise propagating through the channels arising at the outlet of fans, at the inlet and outlet of compressors, are divided into active and reactive (Fig. 46). Active channels are lined with sound-absorbing material. They are used to combat noise with a continuous broadband spectrum. Reactive mufflers are used to combat noise with pronounced discrete components (exhaust of piston internal combustion engines, compressors, etc.) and are made in the form of expansion and contraction chambers, with partitions, etc.

It should be especially noted that traditional methods of dealing with noise using sound insulation and sound absorption are ineffective with infrasound. In this case, the primary concern is the fight against this harmful production factor at the source of its origin.

The main measures to combat infrasound are:

Increasing the speed of machines, which ensures the transfer of the maximum radiation to the region of audible frequencies;

Increasing the rigidity of large structures;

Elimination of low-frequency vibrations;

Installation of jet-type silencers, mainly resonant and chamber.

The main measures to combat ultrasound are to increase operating frequencies; use of sound-insulating covers and screens made of sheet steel

1.5-2 mm thick, covered with a rubber layer up to I mm; elimination of direct contact of workers with a source of ultrasonic vibrations due to mechanization and automation of processes.

5. General methods of dealing with vibration

The main ways to combat vibration are vibration isolation and vibration absorption. The first is based on the reduction of vibration transmitted from machines and mechanisms to the base by placing elastic elements or shock absorbers between them, and the second is based on the dissipation of vibration energy by coatings with high internal friction.

Vibration dampers are made from springs, rubber gaskets, hydraulic or pneumatic devices, or combinations thereof. With vertical vibrations, support or suspended shock absorbers are used, and with the simultaneous action of vertical and horizontal vibrations, a combination of these shock absorbers, placed both vertically and in a horizontal plane. Spring dampers with high vibration-insulating ability and durability have low internal friction, and therefore poorly dissipate vibration energy, the damping of which slows down especially in resonance mode when starting and stopping the machine.

The vibration-insulating ability of rubber shock absorbers is lower than spring ones, but a large internal resistance (coefficient of inelastic resistance) provides a significant decrease in the amplitude of natural vibrations and the time of their damping in resonance modes.

To increase stability and reduce the vibration amplitude of the machine, it should be mounted on a heavy metal frame, thereby increasing the mass of the entire vibration-insulated system, which rests on vibration dampers of the ОВ type.

To reduce vibration of fences, casings, transport and ventilation communications in resonance modes, vibration absorption is used by coating their surfaces with materials with high internal friction (rubber, plastics, mastics). They are applied in places of maximum vibration amplitudes, determined by the values ​​of vibration velocity.

1. Collective and individual protection means against noise and vibration

The applied means of protection against noise and vibration are subdivided into collective protective equipment (RPC) and personal protective equipment (PPE).

Organizational and technical means of protection against noise are associated with the study of the processes of noise production of industrial installations andunits, transport machines, technological and engineering equipment, as well as with the development of more advanced and low-noise design solutions, standards for maximum permissible noise levels of machine tools, units, vehicles, etc.

The most rational method is to combat noise at the source of occurrence (decrease in sound power P). The cause of noise can be mechanical, aerodynamic, hydrodynamic and electromagnetic phenomena due to the design and nature of the operation of machines and mechanisms, as well as inaccuracies made during the manufacturing process and the conditions of testing and operation. To reduce noise at the source of occurrence, the following measures can be successfully applied: replacing shock mechanisms and processes with non-shock ones, for example, replacing a shock film by welding, straightening - by rolling, using a hydraulic drive instead of crank and eccentric drives; the use of low-noise connections, for example, sleeve bearings,

helical, chevron and other special gearing; use as structural materials with high internal friction, for example, replacing metal parts with plastic and other "non-sounding" materials; increased requirements for balancing rotors; changing modes and operating conditions of mechanisms and machines; Applying forced lubrication to joints to prevent wear and friction noise. Timely equipment maintenance is essential to ensure secure attachment and correct joint alignment.

A set of measures aimed at reducing noise in the source can reduce the sound level by 10 - 20 dB (A) or more.

1. Changing the direction of radiation. When designing installations with directional radiation, an appropriate orientation of these installations in relation to workplaces is necessary, since the directivity index can reach 10-15 dB.For example, the opening of the air intake shaft of the ventilation unit must be positioned so that the maximum of the radiated noise is directed towards the anti-noise side of the workplace or residential building.

2. Rational layout of enterprises and workshops. Workplace noise can be reduced by increasing the distance from the noise source to the design point. Inside the building, such rooms should be located away from noisy rooms so that they are separated by several other rooms. On the territory of the enterprise, noisier workshops should be concentrated in one or two places. The distance between quiet rooms (design office, plant management) and noisy workshops should provide the necessary noise reduction.

1. Acoustic treatment of premises. The intensity of noise in rooms depends not only on direct, but also on reflected sound, therefore, sound-absorbing cladding is used to reduce the latter.

surfaces of the room and piece (volumetric) absorbers of various designs, suspended from the ceiling of the premises. The process of absorption of sound occurs by transferring the energy of vibrating air particles into heat due to friction losses in the porous material. For greater efficiency of sound absorption, a porous material should have open pores from the side of sound incidence and open pores.

Reducing noise along the path of its propagation is used when the methods listed above do not provide the required noise reduction. Noise reduction is achieved by reducing the intensity of direct noise by installing soundproof partitions, enclosures, screens, etc. The essence of the soundproofing of the fence is that the energy of the sound wave incident on it is reflected to a much greater extent than it passes through the fence.

Rice. 1. Means of collective protection against noise in the path of its propagation

To combat vibration of machinery and equipment and to protect workers from

vibrations use different methods... The fight against vibration at the source of occurrence is associated with establishing the causes of the appearance of mechanical vibrations and their elimination, for example, replacing crank mechanisms with uniformly rotating ones, careful selection of gears, balancing rotating masses, etc. To reduce vibration, the vibration damping effect is widely used - the conversion of the energy of mechanical vibrations into other types of energy, most often into heat. For this purpose, materials with high internal friction are used in the design of parts through which vibration is transmitted: special alloys, plastics, rubbers, vibration damping coatings. To prevent general vibration, the installation of vibrating machines and equipment on independent vibration damping foundations is used. To reduce the transmission of vibration from sources of vibration to the floor, workplace, seat, handle, etc. methods of vibration isolation are widely used. For this, on the path of vibration propagation, an additional elastic connection is introduced in the form of vibration isolators made of rubber, cork, felt, asbestos, steel springs. Special footwear with massive rubber soles is used as personal protective equipment for workers. Mittens, gloves, liners and pads, which are made of elastic damping materials, are used to protect hands.

Important to reduce the dangerous effects of vibration on the human body is the correct organization of the work and rest regime, constant medical monitoring of the state of health, therapeutic and prophylactic measures such as hydrotherapy (warm baths for hands and feet), massage of hands and feet, fortification, etc. To protect hands from exposure to ultrasound during contact transmission, as well as with contact lubricants, etc. Operators should wear gloves or gloves, anti-moisture or contact lubricant sleeves.

Rice. 2. Classification of methods and means of protection against vibration

Personal protective equipment against noise includes earmolds, headphones and headsets. The effectiveness of personal protective equipment depends on the materials used, construction, pressing force, correct wearing. The earmolds are inserted into the ear canal. They are made from lightweight rubber, resilient plastics, rubber, ebonite and ultra-fine fiber. They reduce the sound pressure level by 10 ... 15 dB. In noisy environments, it is recommended to use earmuffs that provide reliable hearing protection. So, VCNIOT headphones reduce the sound pressure level by 7 ... 38 dB in the frequency range 125 ... 8000 Hz. To prevent the effects of noise with general level 120 dB and above, it is recommended to use headsets that tightly cover the entire parotid region and reduce the sound pressure level by 30 ... 40 dB in the frequency range 125 ... 8000 Hz.

Personal protective equipment for those working against general vibration is used for shoes with shock-absorbing soles.

General technical requirements for special vibration-resistant footwear are introduced by GOST 12.4.024-76. Such shoes are made of leather, artificial, synthetic, textile materials and combined (from these materials). It is designed to protect workers from the effects of general industrial vertical vibration in the frequency range over 11 Hz and is available in the form of boots, half boots and low shoes for men and women. It is designed for individual protection against vibrations and shocks with an energy of 5 J. Along with protection against vibrations, the safety footwear protects the legs of the worker from non-toxic dust and shocks with an energy of up to 50 J (boots and half boots).

The use of a special design of the sole with the use of elastic damping materials makes the shoe effective in vibration protection.

Considerable attention is paid to the protection of hands from vibrations, measures for which are set out in a number of standards. For example, the requirements of GOST 12.4.002-74, GOST 12.4.20-75 apply to personal protective equipment for the hands of a worker from vibration, the protective properties of which are ensured by the use of elastic damping materials. These can be gloves with elastic damping liners; mittens and gloves with soft handhelds; elastic damping pads and plates for wrap around vibrating arms and parts, etc.

The effectiveness of these remedies is determined by the degree to which the level of vibration transmitted to the hands is reduced. It is equal to the difference in levels (or the ratio of absolute values) of vibrational speeds when measured without the use of personal protective equipment and with their use.

Ultrasound protection includes the use of insulating housings and screens, isolation of radiating installations, remote control equipment, and the use of personal protective equipment.

For the localization of ultrasound, it is mandatory to use sound-insulating housings, semi-housings, screens. If these measures do not give a positive effect, then ultrasonic installations should be placed in separate rooms and cabins, lined with sound-absorbing materials.

The most common personal protective equipment when working with ultrasound is anti-noise. To protect hands from exposure to contact ultrasound, it is necessary to use two pairs of gloves - rubber (outer) and cotton (inner) or only cotton.

Requirements for limiting the adverse effects of ultrasound on workers include the following:

Direct contact of a person with the working surface of the ultrasound source and with the contact medium is prohibited. To protect hands from the adverse effects of contact ultrasound in solid, liquid, gaseous media, it is necessary to use sleeves, mittens or gloves (outer rubber and inner cotton);

When systematically working with sources of contact ultrasound for more than 50% of the working time, it is necessary to arrange two regulated breaks - a ten-minute break 1-1.5 hours before and a fifteen-minute break 1.5-2 hours after a lunch break for carrying out physioprophylactic procedures (thermal hydrotherapy , massage, ultraviolet radiation), and remedial gymnastics, fortification, etc .;

Organizational and preventive measures consist in instructing and establishing rational modes of work and rest. To work with ultrasonic sources, persons must be at least 18 years old who have completed the appropriate training course. Persons exposed in the course of their work to the influence of contact ultrasound are subject to preliminary, upon hiring, and periodic

medical examinations.

Reducing the adverse effects of infrasound is achieved by a complex of engineering and medical activities, of which the main ones are: attenuation of infrasound in its source, elimination of the causes of exposure; isolation of infrasound; absorption of infrasound, installation of mufflers; personal protective equipment; medical prevention.

The fight against the adverse effects of infrasound should be carried out in the same directions as the fight against noise. It is most expedient to reduce the intensity of infrasonic vibrations at the design stage of machines or units. Methods that reduce its occurrence and attenuation in the source are of paramount importance in the fight against infrasound.

Ultrasound is a mechanical vibration of an elastic medium propagating in it. Ultrasound includes vibrations with a frequency of more than 20,000 Hz, which are above the hearing threshold and are not perceived by the human ear. The effect of ultrasound on a person is accompanied by structural changes in the brain, autonomic parts of the central and peripheral nervous system, in the walls of blood vessels. Ultrasound is widely used in medicine for treatment and diagnosis, in different areas equipment and industry for analysis and control: defectoscopy, structural analysis of a substance, determination of the physicochemical properties of metals. The widest area of ​​application of ultrasound is technological processes in industry: cleaning and disinfection of parts, mechanical treatment of hard and brittle materials, welding, soldering, tinning, electrolytic processes, acceleration of chemical reactions, etc.

To protect against ultrasound, which is transmitted through the air, a soundproofing method is used. Ultrasonic installations can be located in special rooms.

To protect against ultrasound, which is transmitted through the air, a soundproofing method is used. Ultrasonic installations can be located in special rooms. An effective means of protection is the use of remote-controlled cabins, the location of equipment in soundproofed shelters made of sound-absorbing materials. Ultrasound transmitted by contact is standardized by the "Sanitary Norms and Rules". To protect against ultrasound, which is transmitted through the air, a sound insulation method is used. Ultrasonic installations can be located in special rooms. An effective means of protection is the use of remote-controlled cabins, the location of equipment in soundproofed shelters.

7. Instruments for measuring noise and vibration

The main instruments for measuring noise are sound level meters. In the sound level meter, mechanical sound vibrations perceived by the microphone are converted into electrical ones, which are amplified and then, passing through corrective filters and a rectifier, are recorded by a pointer device. The range of measured total noise levels is usually 30–130 dB with frequency boundaries of 20–16 000 Hz.

To determine the noise spectrum and its levels in octave bands, the sound level meter is connected to filters and analyzers.

Domestic sound level meters Sh-71, PI-14, IShV-1, complete with octave filters, are used for measurements. Acoustic equipment from RFT (Germany) and Brüel & Kjерr (Denmark) has become widespread in our country.

Noise measuring devices consist of a sound level meter (in accordance with GOST 17187-71) and octave electric filters that pass a certain frequency band of electrical oscillations.

The operation of the sound level meter is based on the conversion of sound vibrations by a microphone into electrical vibrations, which, after amplification and passing through octave filters, are transmitted to a measuring device - a dial indicator.

In practice, measuring systems of the ISHV-1 type (with built-in octave filters) from the Vibropribor plant (Taganrog) or the ShVK-1 (with separate FE-2 type filters of the same plant) and 00017 type (with built-in filters) from RFT are used GDR.

To measure only the sound level without frequency analysis, sound level meters of the Shum-1, ShM-1, Sh-63 or 00014 types from RFT (GDR) are used.

For ultrasonic noises (frequency more than 11.2 kHz), the normalized parameters are established by GOST 12.1.001-75 “SSBT. Ultrasound. General safety requirements ".

Vibration is measured with instruments based on mechanical and electrical methods. Electrical measuring instruments provide higher measurement accuracy in a wide range of vibration frequencies of high and low intensity. They allow recording vibrograms at a considerable distance from the vibration object, which ensures safety and convenience in carrying out measurements.

Vibration measurement is carried out in accordance with GOST 12.4.012-75 "SSBT. Means for measuring and controlling vibrations at workplaces. Technical requirements". These requirements are met by a sound level meter of the ShVK-1 type, equipped with a vibration sensor.

For stationary equipment, vibration measurement points are selected at workplaces. The vibration sensor is attached to the work platform or worker's seat. Local vibrations transmitted to the arms when working with hand-held machines are measured by vibration velocity in geometric mean octave bands from 8 to 1000 Hz. The vibration sensor is mounted where hands come into contact with vibrating surfaces. Manual machines must comply

the requirements of GOST 17770-72 “Hand-held machines. Allowable Vibration Levels ".

Conclusion

The factors considered in the lecture - noise, vibration, infrasound and ultrasound - are harmful, negatively affecting performance, causing occupational diseases and other adverse consequences.

Noise is a wave-like propagating mechanical vibrational motion of particles of an elastic (gas, liquid or solid) medium. Its effect on the human body is mainly associated with the use of new, high-performance equipment, with the mechanization and automation of labor processes: the transition to high speeds during the operation of various machines and units. Long-term exposure to noise and vibration on the human body leads to the development of chronic fatigue, contributes to the development of general and occupational diseases, hearing loss, disorders of the central nervous system and the human cardiovascular system.

Infrasound is mechanical vibrations propagating in an elastic medium with frequencies less than 20 Hz, which are below the human hearing threshold. In contrast to noise, infrasound propagates over long distances due to low absorption. Under the influence of infrasound on a person, changes in the rhythms of breathing and heartbeats, indigestion and central nervous system, headaches occur.

In the prevention of the harmful effects of factors, preventive and current sanitary inspections and medical prevention are of great importance.

The main measures to combat noise: elimination of the cause of the noise or its significant attenuation at the very source during the development of technological processes and equipment design; isolation of the noise source from the environment by means of sound - and vibration protection, sound - and vibration absorption; reducing the density of sound energy in rooms, reflected from walls and ceilings; rational layout of premises; the use of personal protective equipment against noise; rationalization of the working regime in conditions of noise; preventive measures of a medical nature. Most effective remedy noise reduction is the replacement of noisy technological operations with low-noise or completely silent. Personal protective equipment (anti-noise) includes earbuds, headphones and helmets.

Means of protection for reducing the level of infrasound: increasing the rotational speed of the shafts to 20 or more revolutions per second; increasing the rigidity of vibrating structures of large sizes; elimination of low-frequency vibrations; making constructive changes to the structure of sources.

Measurement of noise levels is carried out at workplaces or in working areas to compare with the requirements of sanitary standards, as well as to assess the noise characteristics of machines and equipment in order to develop measures to combat noise. Instructions for the measurement and hygienic assessment of noise are given in GOST 12.1.003-76 and GOST 20445-75 “Buildings and structures of industrial enterprises. Method for measuring noise at workplaces ", as well as in the Methodological Guidelines for the Measurement and Hygienic Assessment of Industrial Noises 1844-78 of the USSR Ministry of Health.

For this purpose, the frequency spectrum of the measured sound pressure level in octave frequency bands is used, which is compared with the limiting spectrum normalized in GOST 12.1.003-76 (Table 6.1 is given with abbreviations).

Table 1. Acceptable sound pressure levels and sound levels

Workplaces

Sound pressure levels, dB, in octave bands with geometric mean frequencies, Hz 63, 125, 250, 500, 1000, 2000 4000, 8000

Sound level and equivalent sound level, dBA

Premises of design bureaus, laboratories for theoretical work

Office premises, work rooms

Observation and remote control cabins with voice telephone communication, rooms and areas of precision assembly

Experimental laboratories

For an approximate assessment of the noise situation at the workplace, it is allowed to use a one-number parameter (independent of frequency) as a characteristic of constant noise, the so-called sound level in dBA, measured without frequency analysis - on the A scale of the sound level meter, which approximately corresponds to the frequency response of human hearing.

The characteristic of intermittent noise at workplaces is the equivalent (in terms of energy) sound level in dBA, also determined by the A-scale of the sound level meter.

The human hearing aid is more sensitive to high-frequency sounds, therefore the normalized sound pressure values ​​decrease with increasing frequency.

A characteristic of constant and non-constant (except for fluctuating in time) noises at workplaces are the sound pressure levels in the octave frequency bands from 63 to 8000 Hz.

A characteristic of noise fluctuating in time at workplaces (for example, during the operation of a metal-cutting machine with a variable mode of operation) is the equivalent (in energy) sound level in dBA, determined according to GOST 20445-75 and having the same effect on the hearing aid as a constant noise of the same level.

Main literature:

1. Karakeyan V.I., Nikulina N.M.Life safety. Textbook. - M.-"Yurayt", - 2014

2. Kholostova EI, Prokhorova OG Life safety. Textbook.-

M.- "Dashkov and K", - 2013

Additional literature:

1. Alekseev V.S. Life safety. Lecture notes / V. S. Alekseev, O. I. Zhidkova, N. V. Tkachenko. - M .: Eksmo, 2008 .-- 160 p. S.24-26.

2. Devyasilov V.A. Labor protection: textbook / V.A. Devisilov. - M .: FORUM, 2009 .-- 496 p. S. 145-168.

3. Mikhnyuk T.F. Labor protection: textbook for students / T.F. Mikhnyuk. - Minsk: ITC of the Ministry of Finance, 2010 .-- 320 p. S.111-133.