2-31
Safety notes
2
P/N 6525032M1 - X6
Risks from noise
Noise Characteristics and Measurement
Noise is a pressure variation in an elastic medium, gener-
ally the air, produced by the vibration of a material body
(source) that determines an undesired and often annoy-
ing acoustic sensation. Noise is mainly characterised by:
sound intensity or level: expresses the entity of the
pressure variation due to the sound wave. Measured in
decibels (dB), it doubles the sound intensity and, thus,
the energy that reaches the ear.
frequency: expresses the number of pressure varia-
tions of the wave per second and is measured in Hertz
(Hz) - high-pitched noises have high frequencies (2000-
4000 Hz or more), while low-pitched noises have low
frequencies (250 Hz or less).
How the risk is evaluated
The higher the sound level and exposure time, the greater
the noise risk will be.
Two parameters are used:
LAeq (Equivalent continuous weighted level A): this
is a sound level measurement that takes into account
noise fluctuations and the varying sensitivity of the ear
to the frequencies: LAeq is measured with a sound-level
meter;
PEL (Personal Exposure Level): this is a measurement
that takes the various noise levels into account along
with the time the worker remains on the individual
machines or working at certain processes: PEL is
calculated mathematically.
Noise Pathologies
Damage To The Hearing
Noise causes hypoacusis 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: hypoacusis 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 intoler-
ance to loud noise.
The damage is insidious since it proceeds slowly and
unnoticed: in the initial phase, when it is limited to a di-
minished 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.
Hypoacusis 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 effective means of protection
against it is prevention.
Other Effects
Noise does not just determine aural sensation. For levels
exceeding 70 dBA, it causes stress by means of the
cerebral integration centres and determines a specific
neurovegetative 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 protections 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 attenu-
ating capacities: helmets, ear muffs, ear plugs (Fig.2-50).
Helmets and headsets have the highest dampening ca-
pacity and their use is mandatory when working off road
and noise is over the limits given hereunder.
Earplugs are generally better tolerated and are particularly
useful for prolonged exposition to lower noise levels.
WARNING: It is prescribed that suitable personal hear-
ing protection be used if exposed every day to a noise
level equal or higher than 85 dBA.
Consult the "Technical specifications" section of this
manual in relation to tractor noise measured in in-
stantaneous conditions in compliance with the laws
in force.
WARNING: Do not open the windscreen, the doors or
the side and rear windows during work. The noise in
the cab could rise to such level as to oblige the opera-
tor to wear headsets or other individual protection
against noise.
Fig.2-50
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