chapter 3 ( noise )

7/24/2019 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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chapter 3 ( noise )

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