Since school years, we have become acquainted with such a science as physics. Oscillations, frequencies, acceleration - all these concepts are probably familiar to you. In this article, we will examine in more detail such an important topic as vibration. Each of us is faced with this phenomenon in everyday life.
What is vibration? The definition can be given as follows: these are oscillatory mechanical movements that are transmitted directly to the human body. Its main physical characteristics are the frequency and amplitude of the oscillations. Measurement of vibration in amplitude is carried out in centimeters or meters, and in frequency - in hertz.
How should vibration be measured by acceleration and speed?
With any vibrational motion, speed and acceleration are continuously changing. The acceleration is greatest on the center line of the oscillation, and in extreme positions it is the smallest. Given this, the measurement of vibration is carried out by acceleration and speed. The decibel report is kept from the reference vibration velocity (conditional), which is 5 ∙ 10 8 m / s, as well as vibration acceleration - 3 ∙ 10 4 m / s 2 . Vibration acceleration and vibration velocity are expressed relative to zero thresholds in decibels. The perception threshold in this case is approximately 70 dB. The low-frequency vibration frequency does not exceed 32 Hz, and the high-frequency vibration is more than 32 Hz.
Vibration sources
This is widely used in construction, industry, household, agriculture, transport, electric and pneumatic mechanized hand tools, various equipment and machinery, vehicles, machine tools. Vibration is widely used not only in technology, but also in medicine for the treatment of muscle and nervous diseases (vibration massage, vibration therapy).
Vibration exposure
Vibration is a factor that has great biological activity. The orientation, depth and nature of the physiological shifts of different systems of the human body are determined by its spectral composition, levels and physical properties of the human body. An important role in the genesis of these reactions is played by analyzers - cutaneous, visual, motor, vestibular, etc.
It should be noted the large role played by the biochemical properties of the human body in the subjective perception of vibration. Its effect on the body is mediated by such phenomena as the physical effect of contact on the surface, the spread of tissue vibrations, a direct reaction in tissues and organs to exposure, irritation of mechanoreceptors, which cause subjective and neuroreceptor reactions.
Significant clinical and experimental material on this problem has been accumulated today. The study of vibration showed that motor function disorders arising under its action are caused by both direct muscle damage and impaired regulatory effects of the central nervous system. The prevalence of diffuse shifts in this case can be explained by changes in the functioning of superspinal structures, and the greater severity that local changes have in the muscles is due to their direct trauma. The most sensitive to the effects of local vibration are the departments of the sympathetic nervous system, which regulate the tone of the peripheral vessels, and the departments of the peripheral nervous system, which are associated with tactile and vibrational sensitivity.
The study of vibration has given the right to assert that the parameters of its impact primarily determine the direction of vascular disorders. During mechanical vibrations with a frequency of more than 35 Hz, spastic phenomena occur in the capillaries, and a picture of capillary atony is observed below. The most dangerous from the point of view of the possible development of vascular spasm is the frequency range from 35 to 250 Hz.
Negative impact when performing work operations
Vibration can interfere directly with the performance of work operations, and also indirectly affect a person’s performance, reducing it. Some authors who study vibration consider it to be a strong stress factor that negatively affects psychomotor performance. In addition, mental activity and the emotional sphere suffer, and the likelihood of accidents increases.
Vibration speed
It is established that noise and vibration energetically affect the human body. Therefore, the latter began to be characterized by a spectrum expressed in centimeters per second of the vibrational velocity, or measured in decibels, like noise. Conventionally, a velocity of 5 ∙ 10 6 cm / s was adopted as a threshold value of mechanical vibrations. Only with direct contact of the body with a shaking body or through other solid bodies in contact with it, mechanical vibrations are felt (perceived). In contact with their source, emitting (generating) bass sound, vibration (lowest frequencies), shaking is also perceived with the sound.
General and local
Distinguish between general and local vibration, depending on the distribution of mechanical vibrations in parts of the human body. When local is exposed to concussion, only the part of the body that is in direct contact with the surface that shudders. Most often these are hands. This happens when working with some hand tools or while holding a machine part and other trembling objects.
Local vibration is sometimes transmitted to parts of the body that are connected by the joints to the organs directly exposed to it. But the amplitude of vibrations of these parts of the body is usually lower, because as the vibrations are transmitted through the tissues (especially soft ones), they gradually decay. On the contrary, general vibration affects the whole body. This occurs mainly from mechanical vibrations of the surface where the worker is located.
Vibratory disease
When exposed to vestibular stimuli on the human body, the assessment and perception of time are violated, and the speed of processing information is also reduced. Lack of coordination of movement causes low-frequency vibration. The most pronounced changes are observed at frequencies in the range from 4 to 11 Hz.
Long-term exposure to vibration leads to persistent pathological disorders in the human body. A comprehensive analysis of this pathological process has led to its isolation in a separate nosological form of occupational disease - vibration disease. She continues to hold one of the leading places among other occupational diseases. It is generated by the use of manual machines that do not meet regulatory requirements, as well as the increasing specialization of labor, which leads to an increase in the total time of exposure to mechanical vibrations on the body. With an increase in the duration and intensity of exposure to vibration, the likelihood of developing this disease increases. In this case, individual sensitivity is essential. Overfatigue, cooling, noise, intoxication, muscle tension, etc. increase the harmful effects.
Stages of Vibratory Disease
There are 4 stages of this disease in severity:
- initial (I);
- moderately expressed (II);
- expressed (III);
- generalized (IV, extremely rare).
The negative effects of general vibration
General low-frequency vibration, especially the resonance range, can cause long-term trauma to bone tissue and intervertebral discs, displacement of organs located in the abdominal cavity, as well as lower back pain, degenerative changes in the spine, chronic gastritis, etc.
In women exposed to such exposure for a long time, an increase in the frequency of gynecological diseases, premature birth, and spontaneous abortion is noted. Low-frequency vibration in women causes circulatory disorders in the pelvic organs.
Mechanical vibrations in residential buildings
The study of vibration is very important to carry out not only in industrial buildings, but also in residential buildings. The fact is that it poses a danger not only to the health of workers, but also to some other groups of the population. In residential buildings, the effect of vibration on a person is due to the use of industrial plants, vehicles, engineering and technological equipment. According to the intensity of fluctuations, urban rail transport affects the body most of all: railways, open sections of the subway.
The vibration resulting from the movement of trains in buildings is intermittent and regular. The amplitude of the oscillations decreases with distance from its source. Speaking about the propagation of vibrations along the floors of a multi-storey building, it should be said that the amplification and attenuation of vibration can be observed on the upper ones, depending on the resonance. At the same time, the types of structures of the premises do not have a significant effect on its levels in residential premises under the same conditions of soil. High vibrational levels from engineering and technological equipment (elevators) located in the buildings themselves, as well as built-in objects, are sometimes noted.
Security methods
Vibration protection is very important in enterprises. The rationing of its levels, hygienically justified, is the basis for the prevention of vibrational disease. This takes into account the focus, nature, duration of action. In the Russian Federation, sanitary legislation regulates the levels of mechanical vibrations that must be observed at workplaces.
General vibration protection
The effects of vibration on humans should be reduced to the extent possible. Labor safety is a system of quantitative and qualitative characteristics and indicators that form the specifics of elements that ensure the absence of harmful effects of mechanical vibrations on the human body. Vibration protection is provided by:
- use of vibration-proof machines;
- the use of special means of vibration protection;
- designing production facilities and technological processes that ensure compliance with sanitary standards at workplaces;
- organizational and technical measures, the purpose of which is to improve the operation of used machines, organize their timely repair, as well as control vibration parameters;
- the creation of optimal modes of work and rest.
Personal protective equipment used when exposed to general vibration is vibration-insulating shoes, soles, insoles. The most effective of all remedies can be considered the elimination of direct human contact with trembling equipment. This is done through the use of industrial robots, remote control, replacement and automation of technological operations.
Local vibration protection
Reducing its negative impact is achieved:
- by reducing its intensity directly in the source (the use of handles with shock-absorbing or anti-vibration devices);
- through the use of external protection means, that is, elastic-damping devices and materials placed between the operator’s hands and the source of mechanical vibrations (vibration-proof gloves, mittens, gaskets and inserts).
An important role in the complex of measures aimed at reducing the negative effects of vibration on the human body is assigned to the regimes of work and rest. The total time of contact with her, according to the mode of work, should be limited during the shift. It is recommended to take two breaks for physiotherapy procedures, outdoor activities, etc. The duration of the first should be 20 minutes (this break should be made 2 hours after the start of the shift). The duration of the second is 30 minutes, it should be 2 hours after a lunch break. At the same time, a lunch break should last at least 40 minutes. The duration of continuous one-time exposure to the body of mechanical vibrations should be no more than 10-15 minutes.
The general health and biomedical measures that serve to prevent vibrational illness include the following:
- hydraulic procedures for hands (baths with warm water (+ 37-38 degrees) or the use of dry air heating;
- industrial gymnastics;
- self-massage and mutual massage of the shoulder girdle and hands;
- ultraviolet radiation;
- the use of vitamins, as well as other activities of a general strengthening character (oxygen cocktail, room for psychological relief, etc.).
The importance and relevance of this topic is confirmed by the fact that it is studied at school. Vibration is considered, in particular, in the textbook "Physics" (11th grade). Of course, in school it is studied in a more general way. Considered, in particular, the vibration of the Earth. The frequency of our planet is 7.83 Hz. This quantity is called the Schumann wave, or Schumann resonance frequency. Some, however, believe that the vibration of the Earth has been changing lately. For example, Anku Dinke, a Romanian physicist, believes that by December 2012 they should have reached 12.6-12.8 Hz. Vibrations of a person must correspond to the vibrations of the planet. Those who can tune in to new frequencies will benefit spiritually, as Anku Dinke believes. Human vibration is the topic of a separate article.