chapter 3 ( noise )
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Chapter 3Chapter 3
PollutionPollution
(Noise pollution)(Noise pollution)
iznrh coz u never know who is falling in love with ur smile
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Objectives :Objectives :
At the end of this lesson you should be ableAt the end of this lesson you should be able
to :to :
Dene noise pollutionDene noise pollution
Summarize the sources of noiseSummarize the sources of noiseIdentify the physical properties of soundIdentify the physical properties of sound
Adding and subtracting the sound levelsAdding and subtracting the sound levels
!no" the control of noise pollution!no" the control of noise pollution
Identify the la" that involved in noiseIdentify the la" that involved in noise
pollutionpollution
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Noise pollutionNoise pollution
Dened as un"anted soundDened as un"anted sound
Disagreeable soundDisagreeable sound
http://www.amazon.com/exec/obidos/ASIN/1567665098/philosophyresourhttp://rds.yahoo.com/S=96062883/K=noise+pollution+impact/v=2/SID=e/l=IVI/*-http://www.bmtasia.com.hk/images/noise2.jpg -
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Physical Properties ofPhysical Properties of
SoundSound
A sound "ave is propagates in anA sound "ave is propagates in an
elastic mediumelastic medium
Sound "aves are characterized bySound "aves are characterized by#) $re%uency#) $re%uency
&) amplitude&) amplitude
') avelength') avelength
he %uality of sound is determined byhe %uality of sound is determined by
its fre%uencyits fre%uency
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Physical Properties ofPhysical Properties of
SoundSound Sound po"er* ("att)Sound po"er* ("att)
+ rate of energy is transmitted by+ rate of energy is transmitted by
sound "avesound "ave
Sound Intensity* I ("att,m-&)Sound Intensity* I ("att,m-&)
+ average sound po"er perunit+ average sound po"er perunitarea normal to propagation of aarea normal to propagation of a
soundsound
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The decibelThe decibel
he human ear is able to perceive anhe human ear is able to perceive an
enormous range of sound pressuresenormous range of sound pressures
he sound pressure* S./:he sound pressure* S./:
PaP
P
PL
ref
ref
rms
p
20
log102
2
10
=
=
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Adding and SubtractingAdding and Subtracting
Sound LevelsSound Levels
& method :& method :
0ither0ither1alculation by e%uation1alculation by e%uation
2r2r1alculation "ith using table1alculation "ith using table
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Addition of to sources ofAddition of to sources of
noisenoise
!f the level di"er!f the level di"erbyby
Add the folloingAdd the folloingto the higherto the higher
levellevel
# to $db# to $db 3 db3 db
% to 3 db% to 3 db % db% db
& to ' db& to ' db $ db$ db
$# db and over$# db and over # db# db
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LaLa
0N3I42N50NA/ 67A/I80N3I42N50NA/ 67A/I8
( 5224 309I1/0 N2IS0 )( 5224 309I1/0 N2IS0 )
407/AI2NS* #;=( Act #'; ) ? 4egulations and( Act #'; ) ? 4egulations and
4ules4ules
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(ecibel )d*+(ecibel )d*+
(angerous decibels(angerous decibels
damage to heardamage to hear noise levels @@
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Noise Control ,ethodNoise Control ,ethod 9igh"ay raCc Noise9igh"ay raCc Noise
Noise 4eductionNoise 4eduction
Noise Barrier +Noise Barrier + solid obstructions builtsolid obstructions built
bet"een the high"ay and the homes alongbet"een the high"ay and the homes along
the high"aythe high"ay
reduce noise levels by # to # dBreduce noise levels by # to # dB
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Noise Pollution ControlNoise Pollution Control
Ad-inistrative controlAd-inistrative control (any(any
arrangement that reduces the "orEerFsarrangement that reduces the "orEerFs
eGposure time to noise hazards)eGposure time to noise hazards)
Hob rotationHob rotation
production schedulingproduction schedulingHob redesignHob redesign
appropriate training on noiseappropriate training on noise
9ealth surveillance9ealth surveillancehelps to identify hearing problems sohelps to identify hearing problems so
they can be prevented fromthey can be prevented from
developing furtherdeveloping further
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Noise Pollution ControlNoise Pollution Control
he hierarchy of controlhe hierarchy of control
elimination
substitution
isolation
Engineering control
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SubstitutionSubstitution
Substitute the e%uipment "ith the mostSubstitute the e%uipment "ith the mostsuitable onesuitable one
9" grinder (left) is noisier than 4" one (right)
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!solation!solation
dened as separatingdened as separating
noise sources fromnoise sources frompeople involved inpeople involved inthe "orE or othersthe "orE or othersstanding near bystanding near by
4elocating the noise4elocating the noisesources* operators orsources* operators orothers to positionsothers to positionsa"ay from the noisea"ay from the noisesourcesource
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Personal Protective Equipment (PPE)
A personal hearing protector is a device, or
pair of devices
designed to be worn over or inserted in the
ears of a person to protect hearing.
http://images.google.com.my/imgres?imgurl=http://weblogs.digital.udk-berlin.de/maria/archives/earplugs.jpg&imgrefurl=http://weblogs.digital.udk-berlin.de/maria/archives/2003_12.html&h=308&w=202&sz=20&tbnid=czH3_7mNhgUJ:&tbnh=111&tbnw=73&start=6&prev=/images%3Fq%3Dearplugs%26hl%3Den%26lr%3D%26ie%3DUTF-8 -
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.ngineering control.ngineering control
3ibration Isolation3ibration Isolation
3ibration damping3ibration damping
BarrierBarrier
SilencerSilencer
5uer5uer0nclosure0nclosure
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/ibration isolation/ibration isolation
Reduce noise, impact sound andReduce noise, impact sound andseparate them from disturbingseparate them from disturbing
element.element.
the vibration generator is separatedthe vibration generator is separatedfrom its supporting structure byfrom its supporting structure by
placing an isolator between them.placing an isolator between them.
form of springs, rubber mounts.form of springs, rubber mounts.
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/ibration isolation/ibration isolation
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/ibration (a-ping/ibration (a-ping
JJDampingK refers to property ofDampingK refers to property ofmaterials "hich converts vibrationmaterials "hich converts vibration
energy into heat energyenergy into heat energy
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*arrier*arrier
Noise barriers reduce the sound "hichNoise barriers reduce the sound "hichenters a community from a busy high"ayenters a community from a busy high"ay
by eitherby either
absorbingabsorbing
transmit ? reLecting it bacE acrosstransmit ? reLecting it bacE across
the high"aythe high"ay
or forcing it to taEe a longer pathor forcing it to taEe a longer path
over and around the barrierover and around the barrier
constructed from concrete* masonry*constructed from concrete* masonry*
"ood* metal* and other materials"ood* metal* and other materials
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o eMectively reduce soundo eMectively reduce sound
transmission through the barrier* thetransmission through the barrier* the
material chosen must be rigid andmaterial chosen must be rigid andsuCciently densesuCciently dense
(at least & Eg,s% m)(at least & Eg,s% m)
*arrier*arrier
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*arrier*arrier
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Silencer0(i"userSilencer0(i"user
maEing them ideal for use in partsmaEing them ideal for use in parts
eHection* conveying* drying and cleaningeHection* conveying* drying and cleaningoperationsoperations
DiMuserDiMuser
do not reduce the noisedo not reduce the noise
prevents the generation of noise byprevents the generation of noise by
diMusing high+velocity streamsdiMusing high+velocity streams
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,u1er0.2pansion,u1er0.2pansion
Cha-berCha-berhe reactive eGpansion chamber orhe reactive eGpansion chamber or
muer has no lining of absorptivemuer has no lining of absorptivematerials but attenuates noise bymaterials but attenuates noise by
reLecting the sound "aves so as toreLecting the sound "aves so as tocancel the "aves of the incomingcancel the "aves of the incomingnoise source his process is callednoise source his process is calleddestructive interference 4eactivedestructive interference 4eactive
muers are the types found inmuers are the types found intrucEs and automobilestrucEs and automobiles
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.nclosure.nclosure
.roperty of the enclosure must be.roperty of the enclosure must be
such that it should not be vibratesuch that it should not be vibrate
"hen a sound "ave hits it"hen a sound "ave hits itsurface other"ise the enclosuresurface other"ise the enclosure
itself can become a noise sourceitself can become a noise source
he ideal enclosure is the heavyhe ideal enclosure is the heavyenclosure (materials of highenclosure (materials of high
density)density)
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fans "ere tted "ithfans "ere tted "ithintaEe and eGhaustintaEe and eGhaustsilencers* and ductssilencers* and ducts"ere lined inside"ere lined inside"ith absorptive"ith absorptivebrous material andbrous material and"rapped outside"rapped outside
his reduced thehis reduced thenoise levels fromnoise levels fromaround
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.nclosure.nclosure
Fully enclosed office constructedFully enclosed office constructed
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.nclosure.nclosure
Example of a partial enclosureExample of a partial enclosure
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