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12.1 Effects of Vibration on the Human Body. Hygienical

Estimation of Vibration

Vibration influence on a human depends on:
 the vibration parameters;
 the direction of its action;
 places of its impact;
 the individual characteristics of a person.
Diseases caused by the systematic influence of general vibration:
 vibration illness (a serious disorder of the physical health, usually
caused by the vibration effect onto the CNS);
 migraine;
 dizziness;
 bad sleep;
 lessening of work efficiency;
 bad feel;

 poor cardiac health.
Rate vibration of 10.4 m/s is physiologically caught by a person as the
threshold of perception. Vibration with a speed of 1 m/s causes pain.
General vibration causes the shaking of the whole body. Local vibration
attracts the oscillating movement of the body parts.
To local vibration are exposed workers, who work with different types of hand-
held power tools (for cleaning welds, fettling of castings, riveting, etc.).
The effect of general vibration on the human body occurs in different ways,
depending on its frequency.
The harmful influence of local vibration is as follows: spasms of the vessels
which begin from the finger phalanxes, and spread over the hand, forearm and engulf
the heart vessels.
General vibration with a frequency of 0.7 Hz (shaking), although unpleasant,
but does not lead to disease. In this case, the human body and its individual organs
move as a single unit without experiencing mutual displacements. The consequence
of this vibration is the so-called “sea” disease that occurs due to the disruption of the
normal activities of the human vestibular apparatus.
Various internal organs and body parts (e. g., head and heart) can be
conventionally regarded as oscillatory systems with a specific concentrated mass, as
there is a spring connecting muscles, bones, and connective tissues. This system has a
number of resonances whose frequencies also depend on the worker s body position‟
(“standing” or “sitting”).
The resonance at frequencies of 4–6 Hz corresponds to the oscillations of the
shoulder girdle and hips; at frequencies of 25–30 Hz – head over your shoulders
(sitting position).
For most of the internal organs, natural frequencies are in the range of 6–9 Hz.

Fluctuations jobs with these resonance frequencies are very dangerous because
they can even cause mechanical damage and rupture of these bodies. Systematic
action of general vibration in a resonant or near-resonant frequency may cause
occupational diseases such as vibration disease.

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