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HEARING CONSERVATION

Trina Redford, Industrial HygienistNational Naval Medical Center

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NOISE EVALUATION

OBJECTIVE

To familiarize ourselves with the anatomyand physiologyof the ear

the purposof a noise evaluation tyes of soun! l"l mtrsutilized to collect

measurements

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ANATOMY AND PHYSIOLOGY OF

THE EAR

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Main Components of the

Hearing Mehanism!

"uter #ar

Middle #ar

Inner #ar Central $uditory Nervous %ystem

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%tructures of the "uter #ar

$uricle '(inna) Collects sound

*ocalization

$mlifies sound

'aro+ &-. d/)

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#+ternal $uditory Canal0

$ro+ 1 inch inlength

%3 shaed

*ined with cerumenglands

"uter 145 surrounded6y cartilage

Inner 2457s surrounded6y mastoid 6one

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Mastoi" Proess

/ony ridge 6ehind the

auricle

(rovides suort to

the e+ternal ear and

osterior wall of the

middle ear cavity

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T#mpani Mem$rane!

Thin mem6rane

:orms 6oundary6etween outer and

middle ear ;i6rates in resonse to

sound

Changes acousticalenergy intomechanical energy

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ressure

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Str&t&res of the Inner Ear

Cochlea %nail shaed organ with a

series of fluid-filled tunnels

Converts mechanical energyto electrical energy

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Organ Of Corti!

The end organ of

hearing

Contains stereocilia

and hair cells

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Hair Ce%%s!

:re>uency secific High itches? 6ase of

cochlea

*ow itches? ae+ ofcochlea

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.esti$&%ar S#stem

Consists of three semi-

circular canals

%hares fluid with the

cochlea

Controls 6alance

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Centra% A&"itor# S#stem

;IIIth Cranial nerve or $uditory Nerve3 Carries signals from cochlea to 6rain

$uditory Corte+ Temoral lo6e of the 6rain where sound is

erceived and analyzed

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Ho/ So&n" Tra0e%s Thro&ghHo/ So&n" Tra0e%s Thro&gh

The Ear111The Ear1111Acoustic energy, in the form of sound waves, is channeled into the ear canal 6y

the pinna

2 %ound waves hit the tympani# mm$ranand cause it to vi6rate, li@e a drum,

changing it into mechanical energy

5 The mallus, which is attached to the tymanic mem6rane, starts the ossi#lsinto

motion

! The stapsmoves in and out of the o"al %in!o%of the #o#hlacreating a fluid

motion

& The fluid movement causes mem6ranes in the Organ o& Cortito shear against

the hair #lls

. This creates an electrical signalwhich is sent u the Au!itory Nr"to the 6rain

The 6rain interrets it as soundA

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23ESTIONS4

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NOISE HA5ARDS

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