Ultrasonic protection. Ultrasound protection. Personal noise protection equipment

Ultrasound - acoustic vibrations of air or other elastic medium with a frequency above 20,000 Hz, inaudible to the human ear. Low-frequency ultrasound (up to 100 kHz), propagating by air and contact, is used in the mechanical engineering and metallurgical industries for cleaning, disinfection, crushing and processing of materials; in medicine for cutting tissue, pain relief, sterilization of instruments, medical personnel’s hands and various objects; high-frequency ultrasound (from 100 kHz to 100 MHz and higher), propagating only by contact, is used for flaw detection of castings, welds, and in medicine for the diagnosis and treatment of various diseases (spine, joints, etc.) The therapeutic and preventive stimulating effect of ultrasound has place at ultrasound intensity levels not exceeding 80-90 dB.

Compared to high-frequency noise, ultrasound has a weaker effect on auditory function, but causes pronounced deviations on the part of the vestibular apparatus. Those working with ultrasound equipment may experience occupational pathology in the form of asthenic conditions or asthenovegetative syndrome with dysfunction of the cardiovascular system, and when hands come into contact with sound environment - disorders of the neurovascular system of the hands. With prolonged and intense (120 dB and above) exposure to ultrasound, destruction of bone tissue is observed. Destruction of the bone structure in the growth zone and especially at the tissue interface (bone - periosteum) occurs even under the influence of moderate doses of ultrasound.

The ultrasonic effect on the worker’s body is due to the thermal effect (conversion of ultrasound energy into thermal energy) and the mechanical “cavitation” effect (compression and stretching of tissues, resulting in variable acoustic pressure).

Prevention: application of remote control of ultrasound sources; use of sound-absorbing casings and screens of the generator, cable and ultrasound transducer; parts for ultrasonic cleaning should be immersed in baths in nets with handles with vibration-isolating coatings; organize two regulated breaks: 10 minutes after 1 - 1.5 hours from the start of work before and 15 minutes 1.5 - 2 hours after the lunch break; after work - hand massage, thermal (37-38°C) water procedures, ultraviolet irradiation; use of personal protective equipment - oversleeves, mittens or gloves (outer rubber and inner cotton) and noise protection; introducing into the diet or taking additional amounts of vitamins C and group B; Conducting preliminary and annual periodic medical examinations of workers. Ultrasound MPL in industrial conditions should not exceed 110 dB



Ultrasound is assessed based on its two main parameters: vibration frequency and 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 power of oscillations emitted by a magnetostrictive transducer per unit of irradiated surface - watt per square centimeter (W/cm 2).

When propagating in a liquid medium, ultrasound causes cavitation of this liquid, that is, the formation of tiny empty bubbles in it (due to its periodic compression and rarefaction under the influence of ultrasonic vibrations), immediately filled with vapors of this liquid and substances dissolved in it, and their compression (collapse). This process is accompanied by the formation of noise.

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 turn into concentric waves, filling the entire working room with ultrasound and high-frequency noise.

When working on ultrasonic installations of significant power, workers complain of headaches, which, as a rule, disappear after finishing work; unpleasant noise and squeaking in the ears (sometimes to the point of pain), which persist even after finishing work; fatigue, sleep disturbance (usually drowsiness during the day), sometimes weakened vision and a feeling of pressure on the eyeball, poor appetite, dry mouth and stiff 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) and skin (by 1.0 - 3.0 o), a reduction in pulse rate (by 5 - 10 beats per minute), a decrease in blood pressure - hypotension ( the maximum pressure is up to 85 - 80 mm Hg, and the minimum - up to 55 - 50 mm Hg), somewhat slow reflexes, etc. Workers with extensive experience sometimes exhibit individual health abnormalities, that is, clinical manifestations: emaciation (weight loss up to 5-8 kg), persistent appetite disorder (aversion to food to the point of nausea or insatiable hunger), impaired thermoregulation, innervation of the hands (dulling of skin sensitivity), decreased hearing and vision, dysfunction of the endocrine glands, etc. All these manifestations should be regarded as the result of the combined action of ultrasound and the accompanying high-frequency noise. At the same time, contact irradiation with ultrasound causes faster and more pronounced changes in the body of workers than exposure through the air. As the experience of working with ultrasound increases, the phenomena of its adverse effects on the body also increase. Individuals with up to 2-3 years of experience working in these conditions usually rarely show 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 single and total for a work shift.



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

Ultrasound installations and their individual components (high-frequency current generators, magnetostrictive transducers, baths) must be soundproofed as much as possible by enclosing them in shelters, isolating them in separate cabins or rooms, covering them with soundproofing material, etc. If complete sound insulation is not possible, partial insulation is used, and also sound-absorbing screens and coatings.

Due to the special danger of contact irradiation with ultrasound, the technological process of ultrasonic treatment should completely eliminate the possibility of such exposure or, at least, reduce it to a minimum.

Baths for ultrasonic treatment should be covered with a soundproofing layer on all external surfaces and covered with soundproofing lids during operation. When opening baths to load, unload or change the position of workpieces, the ultrasonic unit must be turned off. It is advisable to block the opening of the bathtub lid with turning off the installation. If it is impossible to completely turn off the ultrasonic units, load parts into the bath in a special metal mesh or basket, and the handles of this basket should not come into contact with the walls of the bath, and especially with the liquid. To change the position of the processed products, the mesh (basket) is removed from the bath.

Installation, rotation and removal of parts in machines for contact ultrasonic processing are also carried out when the machine is turned off. If it is impossible to turn off the installation, these operations are performed with special tongs. Metal and plastic shields are used as reflective screens to prevent the propagation of ultrasonic vibrations.

The most common personal protective equipment when working with ultrasound is noise protection and gloves. It is advisable to have the latter in two layers: rubber on the outside and cotton or wool on the inside; they absorb vibrations better and are waterproof.

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

All newly hired ultrasound workers are subject to a mandatory preliminary medical examination, and subsequently to periodic medical examinations at least once a year.

Ultrasonic vibrations are vibrations with f = 20 kHz. Ultrasound has the same nature as sound.

Sources of ultrasound: equipment in which ultrasonic vibrations are generated to perform technological operations (cleaning and neutralization of parts, flaw detection, welding, drying, technical control) and equipment where ultrasound appears as a related factor.
Ultrasonic vibrations are divided into:
1) low-frequency f  100 kHz (propagation by air and contact) pronounced changes in the state of the nervous, cardiovascular, endocrine systems, metabolism and thermoregulation;
2) high frequency 100 kHz  f  1000000 kHz
Ultrasound with a frequency of 1000 MHz propagates by contact. Here there is a local effect on the human body upon contact with media in which ultrasonic vibrations propagate (ultrasonic vibrations).
Exposure to ultrasonic energy of 6  7 W/cm2 can lead to damage to the peripheral nervous and vascular apparatus at the site of contact (for example, exposure to hands when loading and unloading parts from an ultrasonic bath).
A characteristic of ultrasonic vibrations is the sound pressure level Ly in third-octave bands.
For ultrasound transmitted by contact, the peak value of vibration velocity is normalized.
Ultrasound protection. The following types of ultrasonic protection are used: 1) remote control, 2) automatic blocking when performing auxiliary operations (loading and unloading parts, etc.), source shielding.
Mittens and gloves are used as PPE (for hands).
Ultrasound level control: Measurements are carried out at control points at a height of 1.5 m from the floor, at a distance of 0.5 m from the equipment contour and at least 2 m from the circumferential surfaces. Measurements are carried out at no less than 4 control points along the equipment contour, and the distance between the points is no more than 1 m.
To measure L (sound pressure levels) in air, equipment is used, consisting of a measuring microphone, an electrical circuit with a linear characteristic, a third-octave filter and a measuring device with standard time characteristics.
In the zone of contact with the solid medium, there is a measuring path consisting of a sensor, a laser interferometer, an amplifier, and a signal processing circuit.
Measurements are carried out in the zone of maximum vibration amplitudes.

According to GOST 12.1.001-75, permissible sound pressure levels at workplaces are established: (GOST 12.1.001-75. Ultrasound. General safety requirements. 1982).

For frequency bands with a geometric mean frequency of 12500 Hz, the sound pressure level is 75 dB; for 16000 Hz - 85, for 20000 and above - 110 dB.

Hygienic standardization of air and contact ultrasound. When developing effective preventive measures aimed at optimizing and improving the working conditions of ultrasonic workers, the issues of hygienic standardization of ultrasound as an unfavorable physical factor in the working environment and habitat are put in the first place.

The materials of the comprehensive studies carried out at the State Research Institute of Occupational Medicine of the Russian Academy of Medical Sciences served as the basis for the development of a new system of hygienic regulation of ultrasound, which is reflected in the sanitary standards and rules “Hygienic requirements when working with sources of air and contact ultrasound for industrial, medical and domestic purposes.”

Sanitary norms and rules establish the hygienic classification of ultrasound affecting the human operator; standardized parameters and maximum permissible levels of ultrasound for workers and the population; requirements for control of air and contact ultrasound, preventive measures. It should be noted that these rules and regulations do not apply to persons (patients) exposed to ultrasound for diagnostic and treatment purposes.

Table 12.3. The likelihood of developing polyneuropathy of the hands working with sources of contact ultrasound propagating in liquid and solid media

Standardized parameters air ultrasound are the sound pressure levels in decibels in one-third octave bands with geometric mean frequencies of 12.5; 16; 20; 25; 31.5; 40; 50; 63; 80; 100 kHz.

Standardized parameters contact ultrasound are the peak values ​​of vibration velocity or its logarithmic levels in dB in octave bands with geometric mean frequencies 16; 31.5; 63; 125; 250; 500; 1000; 2000; 4000; 8000; 16,000; 31,500 kHz, determined by the formula:

L v = 20 logV/V0,

V - peak value of vibration velocity, m/s;

V0 is the reference value of vibration velocity, equal to 5?10 -8 m/s.

IN table 12.4 The maximum permissible levels of airborne ultrasound in workplaces and contact ultrasound in areas of contact of hands or other parts of the body working with sources of ultrasonic vibrations or the media in which they propagate are presented.

The new standards are based on the spectral principle, taking into account the combined effects of contact and airborne ultrasound by establishing a reduction correction equal to 5 dB to the MPL of contact ultrasound, which has higher biological activity.

When using ultrasonic sources for household purposes (washing machines, devices for repelling insects, rodents, dogs, security alarms, etc.), usually operating at frequencies below 100 kHz, the standard levels of airborne and contact ultrasound affecting humans are not must exceed 75 dB at the operating frequency.

In addition to sanitary rules and regulations, a number of normative and methodological documents have been developed, regulating, in particular, the working conditions of health workers using ultrasonic sources in the form of equipment, equipment or instruments.

Table 12.4. Maximum permissible levels of ultrasound in workplaces

Note. 1 The maximum permissible levels of contact ultrasound should be taken 5 dB below the tabulated data when workers are exposed to air and contact ultrasound together.

ultrasound diagnostics, organization and conduct of diagnostic studies, as well as sanitary, hygienic and medical preventive measures to limit the adverse effects of contact ultrasound on medical staff. For example, in accordance with hygienic recommendations, the area of ​​the room for ultrasound examinations (ultrasound) should be at least 20 m2, provided that one ultrasound diagnostic unit is placed in it. The room for ultrasound examination must have natural and artificial lighting, a sink with cold and hot water supply, a general supply and exhaust ventilation system with an air exchange rate of 1:3, installation of air conditioners is allowed. In the room, certain microclimate parameters should be maintained: air temperature - 22? C, relative humidity 40-60%, air speed no higher than 0.16 m/s.

When measuring airborne and contact ultrasound generated by household appliances and equipment, the following guidelines must be followed:

comply with the requirements set out in the current sanitary norms and rules.

Preventive actions. Measures to protect workers from the adverse effects of contact ultrasound and related factors in the working environment and labor process include:

1. Medical and biological screening when hiring, taking into account subjective (individual) and objective (occupational) risk factors.

2. The use of various labor regimes (shift and rotating weekly, ten-day, monthly, quarterly, etc.) and a contract system for conducting work for the duration of the projected duration of safety of work experience.

3. Hygienic, including exposure, and clinical and physiological monitoring.

4. Medical and preventive measures to improve the health of workers.

When applying for a job, it is advisable to carry out medical and biological screening in several stages:

Stage I - social selection. According to current hygienic standards and rules, the main contraindication for working under conditions of ultrasound exposure is age under 18 years.

Stage II - medical selection, including a preliminary medical examination and functional studies, taking into account the specifics of the action of contact ultrasound and risk factors (both identified individual and specific professional-production ones established during certification or licensing of the workplace for which employment is expected).

A preliminary medical examination is carried out in accordance with the current order. When conducting preliminary medical examinations, one should take into account contraindications for work in “ultrasonic” professions, which, along with general medical contraindications for admission to work in contact with harmful, hazardous substances and production factors, include chronic diseases of the peripheral nervous system, obliterating diseases of the arteries and peripheral vasospasm.

In addition to medical contraindications, individual and objective risk factors that can aggravate the effects of contact ultrasound have been identified. Subjective (personal) risk factors include a hereditary burden of vascular diseases, an asthenic type of constitution, cold allergies, a history of limb injuries and frostbite, autonomic lability, mainly with a predominance of the tone of the sympathetic nervous system, long work experience in the profession, etc.

Objective or occupational risk factors are high levels of contact and airborne ultrasound, transmission of ultrasonic vibrations through a liquid medium, large area of ​​contact with the source, contamination of hands with contact lubricants, cooling of hands, high ultrasonic index of sources, static load on the muscles of the fingers and hands, forced posture, cooling microclimate, high levels of the total index of single-digit assessment of the complex impact of factors, etc.

Of great importance in the prevention of ultrasonic exposure are rational work regimes established for a specific workplace or vibration source. When developing work regimes, you must be guided by the following principles:

Reducing the total contact time and reducing exposure to ultrasonic sounding when standards are exceeded;

Carrying out work with regularly interrupted ultrasonic influences;

Organization of two regulated breaks, the first - lasting 10 minutes, the second - 15 minutes for active rest, carrying out a special set of industrial gymnastics, physical and preventive procedures, etc. It is rational to arrange the first break 1.5-2 hours after the start of the shift, the second - 1.5 hours after the lunch break;

Lunch break of at least 30 minutes. In addition to shift work schedules, it is advisable to introduce sliding schedules - weekly, ten-day, monthly, quarterly, etc. These modern forms of work regimes are most acceptable for medical workers, when the ultrasonic load on workers, exceeding the permissible one, can be evenly spaced over time.

Measures aimed at increasing the body's resistance, including when exposed to contact ultrasound, include various types of physioprophylactic procedures, reflexoprophylaxis, industrial gymnastics, rational balanced nutrition, vitamin supplementation, and psychophysiological unloading.

Introductory gymnastics is carried out before work and is recommended for all workers without exception. Its main task is to raise the overall tone of the body, activate the activity of organs and systems, help quickly get into the working rhythm and shorten the period of work. The complex includes 7-9 exercises and is performed for 5-7 minutes before starting work.

As a result of numerous experimental studies, the most effective ways to protect workers’ hands from the effects of low-frequency and high-frequency ultrasound propagating in solid and liquid media were selected.

Working with low frequency sources

When vibrations propagate in a solid medium, wear two pairs of thick cotton gloves;

When vibrations propagate in a liquid medium, use two pairs of gloves: the lower ones are cotton and the upper ones are thick rubber.

Working with high frequency sources contact ultrasound is recommended to be used:

When vibrations propagate in a solid environment - one pair of cotton gloves, or cotton gloves with a waterproof palm surface (made, for example, from waterproof synthetic materials), or cotton finger pads;

When vibrations propagate in a liquid medium, use two pairs of gloves: the lower ones are cotton and the upper ones are rubber.

As a means of personal protection against the effects of noise and airborne ultrasound, workers should use noise protection - earplugs, headphones.

Among the measures to protect workers from ultrasonic exposure, an important place is occupied by the issues of training workers in the basics of labor protection legislation and technical rules

safety and preventive measures when working with sources of contact ultrasound; health education among workers, promotion of a healthy lifestyle.

Industrial vibration. Physical characteristics. Sources of industrial vibration. Classification. Effect on the body. Rationing. Control and measurement. Protection from the harmful effects of vibration.

Industrial vibration(mechanical vibrations of solid bodies) is characterized by the frequency of vibrations per second, amplitude, speed and acceleration of the vibrating body. According to the place of application and the degree of distribution in the human body, vibration is conventionally divided into local(or local), extending limitedly to a certain part of the body, most often to the hands of the worker (working with vibrating tools of the impact-rotary type: drilling and jackhammers, vibration compactors) and general, acting on the entire body of the worker.

Vibration can be a cause of occupational disease - vibration disease, the main symptom of which is spasm of small arterioles and precapillaries of the extremities, usually the hands. There are angiotrophic disorders (angioneurosis of the extremities), decreased muscle strength, hand tremors, sluggish tendon reflexes, the development of arthrosis of small joints of the hand, elbow and shoulder joints, and changes in bone tissue. Elasticity decreases and bone fragility increases. Neuromuscular conduction is weakened. With prolonged exposure to vibration, muscle atrophy and an increase in trophic disorders develop. There is an increase in muscle excitability against the background of a decrease in their mineral saturation.

Prevention:improving the design of machines and tools that create vibration in order to reduce the amplitude of vibrations; the use of shock-absorbing pads that dampen vibration; organization of two regulated breaks: 20 minutes 1-2 hours after the start of work and 30 minutes 2 hours after a lunch break of at least 40 minutes using warming; during breaks and after work - warming hydro treatments, gymnastics and hand massage for restoration of blood circulation, ultraviolet irradiation; use of personal protective equipment (mittens, shoes, special suits with vibration-absorbing shock-absorbing materials, which reduces vibration by 10 dB); introducing into the diet or taking additional quantities (50% of the daily requirement) vitamins C, B1, B12 and calcium; Conducting preliminary and annual periodic medical examinations of workers. The MPL of local vibration in industrial conditions varies depending on their frequency characteristics (Table).

Ultrasound normalization.

Ultrasound is also widely used in industry: soldering and welding, mechanical processing of hard and brittle materials, flaw detection.

However, ultrasound has a harmful effect on humans: overheating of body tissues, weakness, fatigue, headaches, ear pain.

According to GOST 12.1.001-75, permissible sound pressure levels at workplaces are established: (GOST 12.1.001-75. Ultrasound. General safety requirements. 1982).

For frequency bands with a geometric mean frequency of 12500 Hz, the sound pressure level is 75 dB; for 16000 Hz - 85, for 20000 and above - 110 dB.

Ultrasonic protection

The harmful effects of ultrasound are reduced due to:

These measures provide protection against ultrasound through the air. Protection from ultrasonic pressure during contact irradiation consists of completely excluding direct contact between workers and tools, liquids and products. Loading and unloading of products is carried out with the ultrasound source turned off, or using tongs with elongated and vibration-isolated handles.

  • - organizational and preventive measures (age limit - 16 years, medical examinations, training and instruction, work and rest schedule);
  • - use of personal protective equipment (rubber gloves).

Special holders and manipulators are used for remote control, since ultrasound affects a person (hands) through solid and liquid media.

Many of the noise control products and measures apply to ultrasound, including personal protective equipment.

Monitoring of sound pressure levels (ultrasound) is carried out after installation of equipment, its repair and periodically, at least once a year, 5 cm from the ear of a person working in his main working position. The time characteristic of the device switches to the “fast” position.

The manufacturer must indicate in the documentation the ultrasonic characteristics of the equipment - sound pressure levels at contact points at a height of 1.5 m from the floor, at a distance of 0.5 m from the contour of the machine and at least 2 m from surrounding surfaces. Measurements are carried out at at least four control points, the distance between which should not exceed 1 m.

Ultrasound as waves is no different from audible sound, but the frequency of the oscillatory process contributes to greater attenuation of vibrations due to the conversion of sound energy into heat. Ultrasound is classified according to its frequency spectrum:

  • for low frequency - oscillations with a frequency of 10 4 ...10 5 Hz;
  • high frequency - 10 5 ... 10 9 Hz.

According to the method of propagation, ultrasound is divided into air and contact.

Sources of ultrasound can be: ultrasonic generators, acoustic transducers, magnetostrictive transducers, piezoelectric transducers. Low-frequency ultrasound is formed during aerodynamic processes.

Ultrasound has mechanical, thermal, physicochemical effects used in industry, technology, biology, medicine, etc. The piezoelectric effect is based on the acoustic action of ultrasound, when, when a quartz plate is deformed, an electric discharge occurs on the edges and is converted into alternating current and vice versa.

Ultrasound is used in the food industry for sterilization, pasteurization and disinfection of products. Ultrasound-treated and then frozen milk does not lose its properties after defrosting. Ultrasonic treatment of milk can significantly reduce the content of harmful microflora in it. The acidity of such milk does not increase within 5 hours. Ultrasound is used in the production of powdered milk, to obtain emulsions of animal fats, spices, aromatic emulsions, and for salting meat. Thanks to ultrasound, it is possible to obtain emulsions from immiscible liquids. Minced meat is treated with ultrasound in the production of sausages, wieners and boiled sausage. When baker's yeast is treated with ultrasound for 1 hour, its fermentation energy increases by an average of 15%; In addition, they increase the content of ergosterol, which is the raw material for obtaining highly active vitamin D.

In confectionery, ultrasound makes it possible to accelerate the process of crystallization of sucrose and obtain a homogeneous mass when making fudge. Under the influence of ultrasound, the specific and taste qualities of chocolate are improved and the duration of its processing in finishing machines is significantly reduced. Ultrasound is used to prepare canned vegetables - puree.

In the fishing industry, ultrasound accelerates the extraction of fat from fish liver, thereby improving the quality of medical fish oil and preserving vitamins A and D that are valuable to humans.

When grape berries are processed with ultrasound, part of the pulp, which previously went to waste, is processed into pure grape juice, which increases the yield of the latter.

Low-frequency ultrasonic vibrations propagate well in the air, having a general effect on the human body; local action occurs upon contact with processed parts and media. Long-term systematic exposure to ultrasound above established standards causes functional changes in the central and peripheral nervous systems, cardiovascular system, endocrine system, and disrupts the functioning of the auditory and vestibular analyzers. Workers experience severe asthenia, vascular hypotension, and decreased electrical activity of the heart and brain. Changes in the central nervous system in the initial phase are manifested by a violation of the reflex functions of the brain (a feeling of fear in the dark, in a confined space, sudden attacks with increased heart rate, excessive sweating, spasms in the stomach, intestines, gall bladder). The most typical are vegetative-vascular dystonia with complaints of severe fatigue, headaches and a feeling of pressure in the head,

difficulty concentrating, inhibition of the thought process, insomnia. The local effect of ultrasound leads to disruption of capillary blood circulation in the hands, damage to the nervous and articular apparatus at the points of contact (vegetative polyneuritis, paresis of the fingers, hands and forearm). Protection against airborne ultrasound can be provided by:

  • using remote control of ultrasound sources, auto-blocking - automatic shutdown of the ultrasound source when performing auxiliary operations;
  • using soundproofing devices (casings, screens) made of sheet steel or duralumin 1 mm thick, coated with sound-absorbing material (roofing felt, technical rubber, Agat type plastics, anti-vibrite), as well as getinax 5 mm thick;
  • installing screens, including transparent ones, between the equipment and the employee;
  • placement of ultrasonic installations in special rooms or cabins, if the measures listed above do not provide the required effect.

To protect hands from the adverse effects of contact ultrasound in solid and liquid media, it is necessary to use mittens or gloves (outer rubber and inner cotton). To reduce the adverse effects of ultrasound during contact transmission in cold and transitional periods of the year, workers should be provided with warm protective clothing.

When systematically working with sources of contact ultrasound for more than 50% of the working time, it is necessary to take two regulated breaks - a ten-minute break 1.5...2 hours after the lunch break, for physiotherapeutic procedures (thermal hydroprocedures, massage, ultraviolet irradiation), and also therapeutic exercises, vitaminization. To protect workers from the adverse effects of airborne ultrasound, noise suppressors should be used.

Persons at least 18 years of age who have completed the appropriate training course and safety instructions are allowed to work with ultrasound sources. Persons exposed to contact ultrasound during work are subject to preliminary, upon hiring and periodic medical examinations.

Ultrasound– these are elastic waves with an oscillation frequency from 20 kHz to 1 GHz, which are not audible to the human ear. Sources of ultrasound are all types of ultrasonic technological equipment; ultrasonic devices and equipment for industrial, medical and household use that generate ultrasonic vibrations in the range from 18 kHz to 100 MHz and higher.

The following types of ultrasound are distinguished:

  • low-frequency (up to 100 kHz) ultrasonic vibrations that propagate by contact and air;
  • high-frequency (100 kHz-100 MHz and higher) ultrasonic vibrations, which propagate exclusively by contact.

Flaw detectors, operators of cleaning, welding, cutting units, medical personnel of physiotherapy rooms and departments, workers of healthcare institutions conducting ultrasound examinations, etc. are exposed to the adverse effects of ultrasound. It has been established that those working with technological and medical ultrasonic sources are exposed to ultrasound with an oscillation frequency of 18 kHz-20 MHz and intensity 50-160 dB.

The impact of ultrasound on the human body

Ultrasonic waves are capable of causing multidirectional biological effects, the nature of which is determined by the intensity of ultrasonic vibrations, frequency, time parameters of vibrations (constant, pulsed), duration of exposure, and tissue sensitivity.

With systematic exposure to intense low-frequency ultrasound, if its level exceeds the maximum permissible level, workers may experience functional changes in the central and peripheral nervous system, cardiovascular and endocrine systems, auditory and vestibular analyzers, and humoral disorders. Data on the effect of high-frequency ultrasound on the human body indicate polymorphic changes in almost all tissues, organs and systems. The changes that occur under the influence of ultrasound (air and contact) follow a general pattern: low intensities stimulate and activate. Medium and large - depress, inhibit and can completely suppress functions. Since 1989, vegetative-sensory polyneuropathy of the hands (angioneurosis), which develops in workers when exposed to contact ultrasound, has been recognized as an occupational disease and included in the list of occupational diseases.

Preventing the adverse effects of ultrasound

Hygienic standardization of air and contact ultrasound is aimed at optimizing and improving the working conditions of workers engaged in performing labor functions with technological and medical ultrasonic sources. Sanitary rules and norms SanPiN 2.2.4/2.1.8.582-96 “Hygienic requirements when working with sources of airborne and contact ultrasound for industrial, medical and domestic purposes” establish the hygienic classification of ultrasound affecting the human operator, standardized parameters and maximum permissible levels of ultrasound for workers and the public, requirements for monitoring airborne and contact ultrasound, as well as preventive measures.

When exposed to contact and airborne ultrasound together, a reduction correction (5 dB) should be applied to the maximum permissible level of contact ultrasound, which has higher biological activity. Levels of airborne and contact ultrasound from household sources (washing machines, devices for repelling insects, rodents, dogs, security alarms, etc.), which operate at frequencies below 100 kHz, should not exceed 75 dB at the operating frequency.

And in order to prevent adverse effects on ultrasound workers, one should also be guided by GOST 12.4.077-79 “SSBT. Ultrasound. Methods for measuring sound pressure at workplaces", GOST 12.2.051-80 "SSBT. Ultrasonic technological equipment. Safety requirements", GOST 12.1.001-89 "SSBT. Ultrasound. General safety requirements" and other regulatory and methodological documents.

Protection from the adverse effects of ultrasound

Protection of workers from the adverse effects of ultrasound is achieved by:

  • conducting preliminary and periodic medical examinations;
  • physioprophylactic procedures (thermal air with micromassage and thermal hydrotherapy for hands, massage of the upper extremities, etc.),
  • reflexology;
  • gymnastic exercises;
  • psychophysical unloading;
  • vitaminization, balanced nutrition;
  • organizing a rational regime of work and rest, etc.

Infrasound protection

Infrasound– these are acoustic vibrations with a frequency below 20 Hz, which are in the frequency range below the threshold of audibility. Industrial infrasound occurs in the same processes as noise of audible frequencies.

Currently, the maximum levels of low-frequency acoustic vibrations from industrial and transport sources reach 100-110 dB. Objects where the infrasound region of the acoustic spectrum predominates over the sound region include automobile and water transport, converter and open-hearth shops of metallurgical production, compressor rooms of gas pumping stations, port cranes, etc.

Features of infrasound

Infrasound as a physical phenomenon obeys the general laws characteristic of sound waves, but has a number of features associated with the low frequency of vibrations of the elastic medium:

  1. It has many times larger oscillation amplitudes than acoustic waves with equal powers of sound sources;
  2. It spreads over long distances from the source of generation due to its weak absorption by the atmosphere.

The large wavelength makes the phenomenon of diffraction characteristic of infrasound (from the Latin diffraclus - broken) - the bending of waves around various obstacles, if the obstacle's size is about the wavelength or larger. Infrasound penetrates rooms and bypasses barriers that block audible sounds. Infrasonic vibrations can cause vibration of large objects due to resonance phenomena. These features of infrasound make it difficult to combat it.

Influencing the human body, infrasound causes unpleasant subjective sensations and numerous reactive changes, which include asthenia, changes in the central nervous, cardiovascular and respiratory systems, and the vestibular analyzer.

The current sanitary rules and norms SanPiN 2.2.4/2.1.8.583-96 “Infrasound in workplaces, in residential and public premises and in residential areas” establish maximum permissible levels of infrasound in workplaces, taking into account the severity and intensity of the work performed:

  • for work of varying severity in industrial premises and on the territory of organizations, the maximum permissible infrasound levels are 100 dB Lin;
  • for work of varying degrees of intellectual and emotional intensity – 95 dB Lean;
  • for time-varying and intermittent infrasound, sound pressure levels should not exceed 120 dB Lin.

Basic methods and means of protection against infrasound

The main methods and means of protection against infrasound are:

  • changing the operating mode of technological equipment - increasing its speed so that the main repetition frequency of power pulses lies outside the infrasonic range;
  • reducing the intensity of aerodynamic processes: limiting vehicle speeds, reducing the flow rate of liquids;
  • interference type mufflers;
  • rational work and rest regime;
  • use of personal protective equipment (mufflers, special belts, etc.).

It is often uneconomical, and sometimes practically impossible, to reduce noise to acceptable levels using general technical measures. For example, in production processes such as riveting, trimming, stamping, cleaning when testing internal combustion engines, etc., personal protective equipment is the main measure to prevent occupational diseases of workers.

Personal protective equipment (anti-noise) includes earplugs, headphones and helmets.

Inserts. These are soft tampons made of ultra-thin fiber inserted into the ear canal, sometimes impregnated with a mixture of wax and paraffin, and hard inserts (ebonite, rubber) in the shape of a cone. Ear buds are the cheapest and most compact means of noise protection, but they are not effective enough (noise reduction is 5-20 dB) and in some cases are inconvenient because they irritate the ear canal.

Headphones. Headphones of the VCIIIOT type are widely used in industry. The headphones fit tightly around the auricle and are held in place by an arched spring. Below is the acoustic characteristics of the VTsNIIOT-2 headphones:

As you can see from here, headphones are most effective at high frequencies, which must be taken into account when using them.

Helmets. When exposed to high noise levels (more than 120 dB), earbuds and headphones do not provide the necessary protection. It is often uneconomical, and sometimes practically impossible, to reduce the noise to acceptable levels using general technical measures. For example, in production processes such as riveting, trimming, stamping, cleaning when testing internal combustion engines, etc., personal protective equipment is the main measure to prevent occupational diseases of workers.

Ultrasound is widely used in the metalworking industry, mechanical engineering, metallurgy, etc. The frequency of ultrasound used is from 20 kHz to 1 MHz, the power is up to several kilowatts.

Ultrasound has harmful effects on the human body. People working with ultrasound equipment often experience functional disorders of the nervous system, changes in pressure, composition and properties of the blood. Complaints of headaches, fatigue, and loss of hearing sensitivity are common.

Ultrasound can act on a person both through the air and through liquid or solid (contact effect on hands).

Sound pressure levels in the frequency range from 11 to 20 kHz should not exceed 75-110 dB, respectively, and the total sound pressure level in the frequency range 20-100 kHz should not exceed 110 dB.

Protection from ultrasound during air irradiation can be provided:

1) by using higher operating frequencies in equipment, for which the permissible sound pressure levels are higher;

2) by making equipment emitting ultrasound in a sound-insulating design (such as casings). Such casings are made from sheet steel or duralumin (1 mm thick) covered with rubber or roofing felt, as well as from getinax (5 mm thick). Elastic casings can be made of three layers of rubber with a total thickness of 3-5 mm. The use of casings, for example, in installations for cleaning parts, reduces the ultrasound level by 20-30 dB in the audible frequency range and 60-80 dB in the ultrasonic range;

3) by installing screens, including transparent ones, between the equipment and the worker;

4) placement of ultrasonic installations in special rooms, enclosures or cabins, if the measures listed above cannot achieve the desired effect.

Protection from the effects of ultrasound during contact irradiation consists of completely eliminating direct contact of workers with tools, liquids and products, since such exposure is the most harmful.