OPERATOR MANUAL |CAPTAIN 273 4WD 37
Noise pathologies
Damage to the hearing
Noise causes hyperdulia or deafness because it destroys the acoustic receptors, nervous cells able to
transform the mechanical sound vibrations into nervous impulses that, on reaching the brain, determine
the aural sensation. These receptors are irreplaceable if they are destroyed and the resulting damage is
irreversible: hyperdulia worsens if exposure to noise continues and does not improve even if this
terminates.
Moreover, it is also bilateral since it can be accompanied by annoying buzzing and whistling sounds,
and by intolerance to loud noise. The damage is insidious since it proceeds slowly and unexpectedly: in
the initial phase, when it is limited to a diminished ability to perceive acute sounds (music, bells) or the
spoken voice when there is a background noise, it can only be detected by means of an audiometric
test. Pulsating noises of great intensity lasting a very short time are highly damaging since the ear is
unable to actuate any physiological protective measures in time. Hyperdulia from noise generally arises
after several years of exposure and depends on the PEL (risk almost null below 80 dBA) and on individual
characteristics. It is an incurable disease: the only efficacious means of protection against it is prevention.
Other effects
Noise does not just determine aural sensation. For levels exceeding* 70dBA, it causes stress by means
of the cerebral integration centers and determines a specific neurovegitative reaction responsible for
effects that lead to cardio circulatory and gastro enteric diseases. Amongst these, it is worthwhile noting:
an increase in gastric acidity, a decrease in the heart rate, visual range and reflex speed; a sensation of
discomfort and weariness with an increased sense of fatigue. These effects are dangerous because they
also increase the risk of accidents. Personal equipment to protect against noise Individual protective
equipment attenuates the sound energy transmitted to the ear through the air. This equipment is used
when dangerous exposure cannot be avoided in any other way.
There are different types of devices with different attenuating capacities:
helmets, ear muffs, ear plugs (Fig.2-33). Helmets and ear muffs offer the
greatest protection but they are bulky and inconvenient to wear. They are
therefore only of use for exposure to high noise levels but for short periods
of time (max. 2 hours).
Ear plugs are generally tolerated to a greater extent and are of particular
use in the case of lengthy exposure to noise of a lesser intensity. Always
use adequate individual protective equipment to safeguard the hearing
when the personal daily level of exposure to noise is 85 dBA or more.
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