The effect of ultrasound on the human body is accompanied by. Is an ultrasonic rodent repeller harmful to humans: myth or truth? Basic information about ultrasound and its sources

The Occupational Safety Control Department continues a series of articles talking about the negative impact of harmful factors on the human body and the fight against it. Today we will talk about ultrasound.

Ultrasounds are mechanical vibrations of an elastic medium that have the same physical nature as sounds, but exceed the upper threshold of audible frequency (over 20 kHz). Low-frequency ultrasounds (frequency - tens of kilohertz) have the ability to propagate in the air, high-frequency (frequency - hundreds of kilohertz) quickly attenuate. In elastic media - water, metal, etc. - ultrasound propagates well, and the speed of propagation is significantly influenced by the temperature of these media.

According to the method of propagation of vibrations, ultrasound is divided into contact (when hands or other parts of the human body come into contact with the ultrasound source) and air (acoustic).

Ultrasound sources in workplaces.

Man-made sources of ultrasound include all types of ultrasonic technological equipment, ultrasonic devices and equipment for industrial, medical and household purposes, which generate ultrasonic vibrations in the frequency range from 20 kHz to 100 MHz and higher. The source of ultrasound can also be equipment, during the operation of which ultrasonic vibrations arise as a concomitant factor.

The main elements of ultrasonic technology are ultrasonic transducers and generators. Currently, ultrasound is widely used in mechanical engineering, metallurgy, chemistry, radio electronics, construction, geology, light and food industries, fishing, medicine, etc. In production conditions, short-term and periodic contact exposure to ultrasound occurs when holding a tool, a workpiece, loading products into baths, unloading them, and other operations.

An analysis of the prevalence and prospects for the use of various ultrasonic sources showed that 60-70% of all those working under the adverse effects of ultrasound are flaw detectors, operators of cleaning, welding, cutting units, ultrasound doctors, physiotherapists, surgeons, etc.

The effect of ultrasound on the human body.

The changes that occur under the influence of ultrasound (air and contact) follow a general pattern: low intensities stimulate and activate, while medium and high intensities depress, inhibit and can completely suppress functions.

The most studied biological effect of ultrasound is its contact effect. The experiment established that ultrasonic vibrations, penetrating deeply into the body, can cause serious local disorders in tissues: an inflammatory reaction, hemorrhages, and, at high intensity, necrosis.

High-frequency contact ultrasound, due to its short wavelength, practically does not propagate in the air and affects workers only when the ultrasound source comes into contact with the surface of the body. Changes caused by the action of contact ultrasound are usually more pronounced in the contact area, most often the fingers and hands.

Long-term work with ultrasound during contact transmission to the hands causes damage to the peripheral neurovascular system, and the severity of the changes depends on the intensity of the ultrasound, the time of sonification and the area of contact, i.e. ultrasonic exposure, and can be enhanced in the presence of concomitant factors in the working environment that aggravate its effect (air ultrasound, local and general cooling, contact lubricants - various types of oils, static muscle tension, etc.).

Among those working with sources of contact ultrasound, a high percentage of complaints was noted about the presence of paresthesia, increased sensitivity of the hands to cold, a feeling of weakness and pain in the hands at night, decreased tactile sensitivity, and sweating of the palms. There are also complaints of headaches, dizziness, noise in the ears and head, general weakness, palpitations, pain in the heart area.

People who have been engaged in experimental work on ultrasound facilities for a long time sometimes experience diencephalic disorders (weight loss, a sharp rise in blood sugar with a slow drop to the initial level, hyperthyroidism, increased mechanical excitability of muscles, itching, paroxysmal attacks such as visceral crises). There are frequent dysfunctions of the peripheral nervous system, numbness, decreased sensitivity of all types like short and long gloves, and hyperhidrosis. Hearing loss and peculiar disorders of the vestibular apparatus are also observed.

Measures to protect and prevent the influence of ultrasound on workers should be aimed at limiting the impact of sound and ultrasonic vibrations transmitted through the air and by contact. The main measure to reduce noise and ultrasound is to reduce their intensity at the source, but this path is not always technically possible. Industrial enterprises often use excessive ultrasonic vibration intensity, so first of all attention should be paid to the rational selection of equipment power. In cases where reducing the intensity is contrary to the interests of the technology, the most effective measure to reduce noise and ultrasound is to soundproof the equipment.

Prevention of contact exposure to ultrasound is achieved by turning off vibrations during the loading and unloading of parts, for which the use of automatic blocking is recommended.

It is possible to significantly reduce the intensity of the contact effect by using special devices for loading parts (grids, plexiglass vessels, etc. with handles with an elastic coating). If periodic short-term contact is necessary, it is recommended to use clamps, forceps, and wear rubber and cotton gloves. Walls and welding machines must have special devices for securing parts during processing.

INFLUENCE OF ULTRASOUND ON THE HUMAN BODY

Currently, ultrasound is widely used in various fields of technology and industry, especially for analysis and control: flaw detection, structural analysis of substances, determination of physical and chemical properties of materials, etc.

Technological processes: cleaning and degreasing of parts, mechanical processing of hard and brittle materials, welding, soldering, tinning, electrolytic processes, acceleration of chemical reactions, etc. use ultrasonic vibrations of low frequency (LF) - from 18 to 30 kHz and high power - up to 6-7 W/cm2. The most common sources of ultrasound are piezoelectric and magnetic transducers. In addition, in industrial conditions, LF ultrasound is often generated during aerodynamic processes: the operation of jet engines, gas turbines, powerful air engines, etc.

Ultrasound has become widespread in medicine for the treatment of diseases of the spine, joints, peripheral nervous system, as well as for performing surgical operations and diagnosing diseases. American scientists have developed an effective method for removing brain tumors (2002) that are not amenable to conventional surgical treatment. It is based on the principle used in cataract removal - crushing the pathological formation with focused ultrasound. For the first time, a device has been developed that can create ultrasonic vibrations of the required intensity at a given point without damaging surrounding tissue. Ultrasound sources are located on the patient's skull and emit relatively weak vibrations. The computer calculates the direction and intensity of the ultrasound pulses so that they merge with each other only in the tumor and destroy tissue.

In addition, doctors have learned to re-grow lost teeth using ultrasound (2006). Low-intensity pulsating ultrasound stimulates the regrowth of knocked out and lost teeth, researchers from Canada's University of Alberta have discovered. Doctors have developed a special technology - a miniature “system on a chip” that ensures the healing of dental tissue. Thanks to the wireless design of the ultrasound transducer, a microscopic device equipped with biologically compatible materials is placed in the patient’s mouth without causing discomfort.

Diagnostic ultrasound has been intensively used for three decades during pregnancy and for diseases of individual organs. Ultrasound, encountering an obstacle in the form of human or fetal organs, determines their presence and size.

British researchers from the University of Leicester have used ultrasound technology in an automated machine that takes a customer's measurements to make bespoke clothes. In the installation, an ultrasound source and sixty sensors record signals reflected by the surface of the body.

For these purposes, technology uses sound vibrations of high frequency (HF) - from 500 kHz to 5 MHz and low power - from 0.1 to 2.0 W/cm 2. The intensity of the therapeutic ultrasound used most often does not exceed 0.2-0.4 W/cm 2 ; The frequency of ultrasound vibrations used for diagnostics ranges from 800 kHz to 20 MHz, the intensity varies from 0.01 to 20 W/cm2 or more.

These are just some of the applications of ultrasound. A person is exposed to it in all cases. How does ultrasound affect the human body? Is it harmful?

Ultrasound is mechanical vibrations of an elastic medium, propagating in it in the form of alternating compressions and rarefaction; with a frequency above 16-20 kHz, not perceptible to the human ear.

As the frequency of ultrasonic vibrations increases, their absorption by the environment increases and the depth of penetration into human tissue decreases. Absorption of ultrasound is accompanied by heating of the medium. The passage of ultrasound in a liquid is accompanied by the effect of cavitation. The ultrasound generation mode can be continuous or pulsed.

In addition to the general effect on the body of those working through the air, LF ultrasound has a local effect upon contact with workpieces and environments in which ultrasonic vibrations are excited. Depending on the type of equipment, the area of greatest impact of ultrasound is the hands. Local action can be permanent (holding the tool against the workpiece during tinning, soldering) or temporary (loading parts into baths, welding, etc.).

Exposure to powerful installations (6-7 W/cm2) is dangerous, because it can lead to damage to the peripheral nervous and vascular apparatus at the points of contact (vegetative polyneuritis, cuts in the fingers, hands and forearms). Contact exposure to ultrasound most often occurs during the loading and unloading of parts from ultrasonic baths. A three-minute immersion of fingers in bath water with a transformer power of 1.5 kW causes a tingling sensation, sometimes itching, and after 5 minutes. after the cessation of the ultrasound, a feeling of cold and numbness of the fingers is noted. Vibration sensitivity decreases sharply, and pain sensitivity in different individuals can be either increased or decreased. Short-term systematic contact with a sound environment lasting 20-30 s or more in such installations can already lead to the development of the phenomena of vegetative polyneuritis.

Consequences of ultrasound exposure on the body: functional changes in the central and peripheral nervous system, cardiovascular system, auditory and vestibular analyzer, endocrine and humoral deviations from the norm; headaches with predominant localization in the frontonasal orbital and temporal regions, excessive fatigue; feeling of pressure in the ears, unsteadiness of gait, dizziness; sleep disturbance (drowsiness during the day); irritability, hyperacusis, hyperosmia, fear of bright light, increased pain excitability thresholds; under conditions of exposure to intense ultrasound accompanied by noise - insufficiency of vascular tone (lowering blood pressure, hypotension), disinhibition of skin-vascular reflexes in combination with a strong vasomotor reaction; general cerebral disorders; vegetative polyneuritis of the hands (less often of the feet) of varying degrees (pasty, acrocyanosis of the fingers, thermal asymmetry, sensory disorder similar to gloves or socks); increased body and skin temperature, decreased blood sugar levels, eosinophilia. The severity of pathological changes depends on the intensity and duration of ultrasound; contact with a sound environment and the presence of noise in the spectrum also worsen health.

Compared to HF noise, ultrasound has a noticeably weaker effect on auditory function, but causes more pronounced deviations from the norm in vestibular function, pain sensitivity and thermoregulation. Intense HF ultrasound upon contact with the surface of the body causes essentially the same disturbances as LF.

Particular attention should be paid to diagnostic ultrasound. Kruskal's review of Diagnostic Imaging in Pregnancy (2000) noted that ultrasound waves have the potential to cause damage to biological tissue through heating and cavitation. However, there is no documented evidence of the biological effects of ultrasound. The Canadian Society of Obstetricians and Gynecologists noted in a 1999 statement that there is no scientific evidence that diagnostic ultrasound is harmful to the developing fetus. It has previously been suggested that ultrasound exposure may be associated with low birth weight, dyslexia, increased rates of leukemia, solid tumors, and learning delays in reading and writing. The risk of ultrasound examination consists mainly of possible overdiagnosis or the possibility of missed pathology.

Permissible sound pressure levels of ultrasonic installations should be taken in accordance with “Sanitary norms and rules for working on industrial ultrasonic installations” No. 1733-77, GOST 12. 1. 001-89, SanPiN 2. 2. 2/2. 1. 8. 582, which are given for 1/3 octave bands in the frequency range 1.25-100 kHz and amount to 80 - 110 dB. During contact action, the ultrasound level should not exceed 110 dB. GOST provides for changes in the ultrasonic maximum level with a total reduction in the time of its exposure (by 6 dB with an exposure time of 1... 4 hours per shift and 24 dB with an exposure time of 1... 5 minutes).

The prevention of the harmful effects of ultrasound is based on technological measures: the creation of automatic ultrasonic equipment (for washing containers, cleaning parts), installations with remote control; transition to the use of low-power equipment. In this case, the intensity of ultrasound and noise is reduced by 20-40 dB (for example, during ultrasonic cleaning of parts, soldering, drilling, etc.).

When designing ultrasonic installations, it is advisable to choose operating frequencies that are as far as possible from the audible frequency range (not lower than 22 kHz) in order to avoid the effects of pronounced HF noise.

Ultrasonic installations with noise and ultrasound levels exceeding the standards should be equipped with sound-insulating devices (casings, screens) made of sheet steel or duralumin coated with sound-absorbing materials (roofing felt, technical rubber, plastic, anti-vibrite, getinax, anti-noise mastic). Soundproofing covers of ultrasonic installations must be insulated from the floor with rubber gaskets and have no cracks or holes.

Installations that generate vibrations with a total level of 135 dB are placed in soundproofed cabins. To eliminate the impact of ultrasound upon contact with liquid and solid media, it is necessary to turn off the ultrasonic transducers; the use of a special working tool with a vibration-isolating handle and protection of hands with rubber gloves with a cotton lining. At an increased level of vibration velocity in the frequency range from 8 to 2000 Hz on the surfaces of ultrasonic tools (soldering irons, welding guns, etc.) and devices for fixing parts, it is necessary to resort to damping coatings.

The installations are located in isolated rooms; separated by partitions covering the entire height of the room; are fenced in the form of booths, boxes, enclosures in order to reduce noise and ultrasound at workplaces to acceptable values. ; workers should use personal protective equipment.

When using HF ultrasound, measures should be aimed at protecting the hands of workers. When working in a liquid environment in a laboratory or when performing underwater massage in physiotherapy rooms, contact with liquid must be completely excluded. During flaw detection, workers must avoid touching their hands with the piezoelectric element of flaw detection equipment.

The manufacturer must indicate in the operational documentation of the production equipment an ultrasonic characteristic - sound pressure levels in one-third octave bands of the accepted frequency range, measured at control points around the equipment; operating mode in which ultrasonic characteristics should be determined. Those working with ultrasonic equipment are instructed on the nature of the action of ultrasound; protective measures; conditions for safe maintenance of ultrasonic installations.

Contraindications for employment: chronic diseases of the central and peripheral nervous system, neuritis, polyneuritis; general and vascular neuroses; previous skull injuries (concussion); metabolic and endocrine disorders; labyrinthopathy and chronic diseases of the hearing organ; persistent hearing loss of any etiology; hypotension and hypertension. Periodic medical examinations should be carried out once a year with the participation of a neurologist, therapist, otolaryngologist; It is important to study the vestibular apparatus.

Thus, ultrasound, on the one hand, is widely used in many areas of the economy, on the other hand, its effect on the human body during therapeutic use has not yet been sufficiently studied. Clinic patients undergoing diagnostics of diseases using ultrasound are poorly informed about possible harm to health. At least educational work should be carried out in this direction.

Table of contents
Page
Introduction…………………………………………………………….…..………..3
1. “Ultrasound” and its application in medicine………………………………………………………4
1.1. How does “ultrasound” affect the human body……………………………….5
1.2. Consequences of ultrasound exposure on the body………………………8
2. Warnings of the harmful effects of ultrasound………………………………...9
2.1. Contraindications for employment………………………………….11
Conclusion……………………………………………………………… ……………………………12
Bibliography…………………………………………………. .13

Introduction

The scope of application of ultrasound today is unusually wide. This includes navigation, industry, medicine and much more. Is ultrasound harmful to humans? Judging by the fact that in medicine ultrasound is used not only for diagnosis, but also for treatment, we can answer that no, it is not harmful. But this is not entirely accurate. As in many other things, it is important to know the limit here; in our case, the measure is volume. Ultrasound, like the sounds we hear, has volume. Doctors consider a safe volume of 80-90 dB; ultrasound volume above 120 dB with prolonged exposure has a negative effect on human health.

Technological processes: cleaning and degreasing of parts, mechanical processing of hard and brittle materials, welding, soldering, tinning, electrolytic processes, acceleration of chemical reactions, etc. use ultrasonic vibrations of low frequency (LF) - from 18 to 30 kHz and high power - up to 6 -7 W/cm 2 . The most common ultrasound sources are piezoelectric and magnetic transducers. In addition, in industrial conditions, LF ultrasound is often generated during aerodynamic processes: the operation of jet engines, gas turbines, powerful air engines, etc.

1. “Ultrasound” and its application in medicine

Ultrasound– these are mechanical vibrations of an elastic medium, propagating in it in the form of variable compression and rarefaction; with a frequency above 16-20 kHz, not perceptible to the human ear.
As the frequency of ultrasonic vibrations increases, their absorption by the environment increases and the depth of penetration into human tissue decreases. Absorption of ultrasound is accompanied by heating of the medium. The passage of ultrasound in a liquid is accompanied by the effect of cavitation. The ultrasound generation mode can be continuous or pulsed.

1.1. How does ultrasound affect the human body?

Exposure to powerful installations (6-7 W/cm2) is dangerous because it can lead to damage to the peripheral nervous and vascular apparatus at the points of contact (vegetative polyneuritis, cuts in the fingers, hands and forearms). Contact exposure to ultrasound most often occurs during loading and unloading of parts from ultrasonic baths. A three-minute immersion of fingers in bath water with a converter power of 1.5 kW causes a tingling sensation, sometimes itching, and after 5 minutes. after the cessation of the ultrasound, a feeling of cold and numbness of the fingers is noted. Vibration sensitivity decreases sharply, and pain sensitivity in different individuals can be either increased or decreased. Short-term systematic contact with the sounded environment lasting 20-30 s or more in such installations can already lead to the development of the phenomena of vegetative polyneuritis.

Particular attention should be paid diagnostic ultrasound. Kruskal's review of Diagnostic Imaging in Pregnancy (2000) noted that ultrasound waves have the potential to cause damage to biological tissue through heating and cavitation. However, there is no documented evidence of the biological effects of ultrasound. The Canadian Society of Obstetricians and Gynecologists noted in a 1999 statement that there is no scientific evidence that diagnostic ultrasound is harmful to the developing fetus. It has previously been suggested that ultrasound exposure may be associated with low birth weight, dyslexia, increased rates of leukemia, solid tumors, and learning delays in reading and writing. The risk of ultrasound examination consists mainly of possible overdiagnosis or the possibility of missed pathology.

Under the influence of ultrasound, the permeability of cell membranes for various biologically active substances involved in metabolic processes, the speed of enzymatic processes, the electrical activity of tissue cells and some other processes change. In tissues under the influence of ultrasound, metabolic processes are activated, the content of nucleic acids increases and the processes of oxygen absorption by tissues are stimulated.

Under the influence of ultrasound, it increases the permeability of blood vessels, so in case of an acute inflammatory process with severe tissue swelling, the course of the disease may worsen. But in subacute and chronic inflammatory processes that are not accompanied by edema, improvement occurs, since ultrasound promotes resorption of the process. A pronounced antispasmodic (relieving spasms of the smooth muscles of internal organs and the walls of blood vessels) effect of ultrasound has also been established.

Ultrasound promotes less rough scarring of wounds and inflammatory processes, and also leads to the softening of already formed scar tissue, which makes any scars less rough and noticeable after ultrasound treatment. Therefore, phonophoresis is used in the treatment of the consequences of various injuries, as well as adhesions after surgery and inflammatory diseases.

Small doses of ultrasound have a stimulating effect on tissue restoration processes, while large doses inhibit these processes. Ultrasound inhibits the conduction of pain impulses in nerve cells and nerve fibers, which makes it possible to use it for various pain syndromes.

Ultrasound has a stimulating effect on the endocrine system: the content of insulin and glucocorticoids in the blood increases.

Under the influence of ultrasound, both local tissue changes occur (activation of local metabolic processes, improvement of blood circulation in small blood vessels, restoration processes) and complex reactions of the whole organism, as a result of which an increase in the body’s defenses and restoration processes in the body as a whole occurs.

1.2. Consequences of ultrasound exposure on the body

Functional changes in the central and peripheral nervous system, cardiovascular system, auditory and vestibular analyzers, endocrine and humoral deviations from the norm. Headaches with predominant localization in the frontonasal orbital and temporal regions, excessive fatigue. Feeling of pressure in the ears, unsteadiness of gait, dizziness; sleep disturbance (drowsiness during the day); irritability, hyperacusis, hyperosmia, fear of bright light, increased pain excitability thresholds; under conditions of exposure to intense ultrasound accompanied by noise - insufficiency of vascular tone (lowering blood pressure, hypotension), disinhibition of skin-vascular reflexes in combination with a strong vasomotor reaction; general cerebral disorders; vegetative polyneuritis of the hands (less often of the feet) of varying degrees (pasty, acrocyanosis of the fingers, thermal asymmetry, sensitivity disorder like gloves or socks); increased body and skin temperature, decreased blood sugar, eosinophilia. The severity of pathological changes depends on the intensity and duration of ultrasound; contact with a sound environment and the presence of noise in the spectrum also worsen health.

2. Warnings of the harmful effects of ultrasound

The prevention of the harmful effects of ultrasound is based on technological measures: the creation of automatic ultrasonic equipment (for washing containers, cleaning parts), remote-controlled installations; transition to the use of low-power equipment. In this case, the intensity of ultrasound and noise is reduced by 20-40 dB (for example, during ultrasonic cleaning of parts, soldering, drilling, etc.).

Ultrasonic installations with noise and ultrasound levels exceeding the standards should be equipped with sound-insulating devices: casings, screens made of sheet steel or duralumin. Covered with sound-absorbing materials: roofing felt, technical rubber, plastic, anti-vibration, anti-noise mastic. Soundproofing covers of ultrasonic installations must be insulated from the floor with rubber gaskets and have no cracks or holes.
etc.................

Ultrasonic repellers have recently received widespread practical use. They are very often used to combat various rodents, insects, and stray animals. It turns out that ultrasound waves can cause discomfort, pain, panic and fear.

Ultrasonic rodent repellers

But at the same time, the natural question is whether an ultrasonic rodent repeller is harmful to humans. Let's consider what ultrasound is and how it affects the human and animal body. This will allow you to make the right decision for yourself whether or not to use ultrasonic repellers at home.

To figure out whether an ultrasonic repeller is dangerous for people, let’s consider what an ultrasonic wave is. Ultrasound refers to the category of sound waves, which are vibrations of the molecules of the medium in which they propagate. Through these waves, sound information is transmitted to the auditory organs.

A feature of ultrasonic waves is their high frequency and short wavelength. As a result, they have high penetrating ability.

The frequency range occupied by ultrasonic waves ranges from 20 to 70 kHz. This range is “inaudible to humans” because the human ear can perceive sound waves in the range of values from 10 Hz to 16 kHz.

In what areas is KM still used?

In addition to ultrasonic repellers, ultrasound has wide practical applications in various fields of human activity.

Among the main ones, the following should be highlighted:

diagnostic procedures in medicine;
echolocation;
use for flaw detection;
implementation of therapeutic techniques during treatment;
use in production processes;
use for preparing various mixtures;
use for ultrasonic welding;
application in electroplating;
for carrying out various scientific research.

To conclude whether ultrasonic repellers are harmful to humans, let’s consider the impact of ultrasound on human and animal health. As described above, a person cannot hear ultrasonic waves, since his hearing aid is designed for a completely different range - 10 Hz...16 kHz. As a result, a person will not feel any irritability or discomfort when he is near a working repeller.

When characterizing sound waves, it is important to remember not only the frequency, but also the pressure that the sound creates. Modern ultrasonic repellers generate ultrasonic waves, the pressure of which is in the range of 72...100 dB.

This pressure level is safe for a person whose hearing aid normally perceives waves with sound pressure up to 100 dB. If the pressure is high, painful symptoms may occur. Therefore, the ultrasonic mouse repeller will not have any effect on humans.

But with rodents and some animals things are completely different. Their hearing aid is just capable of perceiving ultrasonic waves. Therefore, they may seem like a noise irritant to them.

But this is only half the trouble - it turns out that sound pressure, which does not cause harm to humans, has a detrimental effect on rodents. Their hearing aid is so sensitive that an ultrasound wave with a pressure of 70 dB or more will cause painful sensations in rodents.

As a result of this effect, rodents will feel pain, fear, discomfort and anxiety when they enter the area of influence of the device. These factors lead to the fact that rodents try to leave occupied territories as quickly as possible.

As for pets, ultrasound does not affect them, just like people. The only exceptions are those animals that are classified as rodents - guinea pigs, hamsters, tame rats, etc. However, this does not mean that any repeller can be installed in rooms where pets are located.

There are models that use not only ultrasonic waves, but also ordinary sound waves in their work. This type of device will cause discomfort for both pets and humans. Therefore, ultrasonic devices can only be used in strict accordance with the instructions and recommendations of the manufacturer.

Conclusion

Having studied how an ultrasonic repeller acts on the human body and on rodents, we can conclude that these devices are completely safe and cannot cause harm to health. For this to happen, it is important to choose the right repeller.

Today, there are models that can be used in residential premises, and there are devices that are designed for objects where there are no people. Therefore, the choice of a repeller is important to ensure that it does not harm a person.

Ultrasound has a mainly local effect on the body, since it is transmitted through direct contact with an ultrasonic instrument, workpieces or environments where ultrasonic vibrations are excited. Ultrasonic vibrations generated by ultrasonic low-frequency industrial equipment have an adverse effect on the human body. Long-term systematic exposure to airborne ultrasound causes changes in the nervous, cardiovascular and endocrine systems, auditory and vestibular analyzers, and humoral disorders. The most characteristic is the presence of vegetative-vascular dystonia and asthenic syndrome.

The degree of severity of the changes depends on the intensity and duration of exposure to ultrasound and increases in the presence of high-frequency noise in the spectrum, while a pronounced hearing loss is added. If contact with ultrasound continues, these disorders become more persistent.

Under the influence of local ultrasound, in addition to general cerebral disorders, phenomena of vegetative polyneuritis of the hands (less often of the legs) of varying degrees of severity occur, up to the development of paresis of the hands and forearms, vegetomyofasciculitis of the hands and vegetative-vascular dysfunction.

The nature of the changes that occur in the body under the influence of ultrasound depends on the dose of exposure.

Small doses - sound level 80 - 90 dB - give a stimulating effect - micromassage, acceleration of metabolic processes.

The effect on tissue is limited to irritation of nerve receptors. Changes in the functional state of the central nervous system are accompanied by normalization of vascular reactions, a decrease in blood pressure, and vasodilation. Large doses - sound levels of 120 dB or more - have a damaging effect.

Improving working conditions

The basis for preventing the adverse effects of ultrasound on persons servicing ultrasonic installations is hygienic regulation.

In accordance with GOST 12.1.01 - 83 (SSBT. Ultrasound. General safety requirements), “Sanitary norms and rules for working on industrial ultrasonic installations”, sound pressure levels in the high-frequency region of audible sounds and ultrasounds at workplaces are limited (Table 11) .

Table 11. Acceptable ultrasound levels

Ultrasound transmitted by contact is regulated by “Sanitary norms and rules for working with equipment that creates ultrasound transmitted by contact to the hands of workers” No. 2282 - 80. The peak value of vibration velocity in the frequency band 0 is set as a standardized parameter of ultrasound transmitted by contact. ,1 - 10 MHz or in dB relative to 5*10 -8 m/s. The maximum value of ultrasound in the area of contact of the operator’s hands with the working parts of the devices during an 8-hour working day in terms of vibration velocity should not exceed 1.6 * 10 -2 m/s or 110 dB.

Ultrasound is allowed for contact transmission by intensity in W/cm 2. The maximum permissible value is 0.1 W/cm2. Measures to prevent the adverse effects of ultrasound on the body of operators of technological installations and personnel of treatment and diagnostic rooms consist primarily of carrying out measures of a technical nature. These include the creation of automated, remote-controlled ultrasound equipment; using low-power equipment whenever possible, which helps reduce the intensity of noise and ultrasound in the workplace by 20 - 40 dB; placement of equipment in soundproof rooms or remote-controlled rooms; equipment of soundproofing devices, casings, screens made of sheet steel or duralumin, coated with rubber, anti-noise mastic and other materials.

When designing ultrasonic installations, it is advisable to use operating frequencies that are farthest from the audible range - not lower than 22 kHz.

To eliminate the effects of ultrasound upon contact with liquid and solid media, it is necessary to install a system for automatically shutting off ultrasonic transducers during operations during which contact is possible (for example, loading and unloading materials). To protect hands from the contact action of ultrasound, it is recommended to use a special working tool with vibration-isolating handle.

If, for production reasons, it is impossible to reduce the level of noise and ultrasound intensity to acceptable values, it is necessary to use personal protective equipment - noise protection, rubber gloves with cotton lining.

Organizational and medical-preventive measures. Organizational measures include compliance with the work and rest schedule and the prohibition of overtime work. When in contact with ultrasound for more than 50% of the working time, breaks of 15 minutes are recommended every 1.5 hours of work.

A significant effect is achieved by a complex of physiotherapeutic procedures - UV irradiation, water procedures, vitaminization, etc.

Workers must undergo preliminary and periodic medical examinations in accordance with the order of the USSR Ministry of Health (No. 700). Persons under 18 years of age, as well as persons who have contraindications to work under ultrasound conditions, are not allowed to work with ultrasound.

All workers must be familiar with the “Hygienic requirements for the design and operation of ultrasonic installations”, approved by the SSEU of the USSR Ministry of Health dated December 30, 1969, and trained in safe labor practices.