MCCORMICK X60 Series - How the Risk Is Evaluated; Personal Equipment to Protect against Noise; Noise Pathologies; Damage to the Hearing

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Safety notes
Risks deriving from exposure to
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characterized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Herz
(Hz)-acute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determined 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:hypacusia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
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.
Hypacusia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protec-
tion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 centers and determines a specific
neurovegetativereactionresponsibleforeffectsthatlead
tocardiocirculatoryandgastroenteric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attenuat-
ingcapacities:helmets,earmuffs,earplugs(Fig.2-42).
Helmetsandheadsetshavethehighestdampeningcapac-
ityandtheiruseismandatorywhenworkingoffroadand
noiseisovertheabovelimits.
Earplugsaregenerallybettertoleratedandareparticularly
usefulforprolongedexpositiontolowernoiselevels.
CAUTION: It is prescribed that suitable personal
hearing 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 instantaneous conditions in compliance with the
laws in force.
CAUTION: 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
operator to wear headsets or other individual pro-
tection against noise.
Helmetsandheadsetshavethehighestdampeningcapac-
ityandtheiruseismandatorywhenworkingoffroadand
noiseisovertheabovelimits.