1

PART9.4:BUILDINGSERVICESACOUSTICS,SOUNDINSULATION ANDNOISECONTROL

CONTENTSPage

9.4.1SCOPE2

9.4.2DEFINITIONS2

9.4.3PLANNINGANDDESIGNAGAINSTOUTDOORNOISE9

9.4.4PLANNINGANDDESIGNAGAINSTINDOORNOISE15

9.4.5RESIDENTIALBUILDINGS16

9.4.6EDUCATIONALBUILDINGS19

9.4.7HOSPITALBUILDINGS24

9.4.8OFFICEBUILDINGS27

9.4.9HOTELSANDHOSTELS32

9.4.10INDUSTRIALBUILDINGS34

9.4.11LABORATORIESANDTESTHOUSES42

9.4.12MISCELLANEOUSBUILDINGS43

9.12.13NOISEFROMBUILDINGSERVICES47

APPENDIXA48

APPENDIXB51

APPENDIXC55

APPENDIXD57

APPENDIXE58

APPENDIXF60

APPENDIXG73

APPENDIXH73

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PART9.4:BUILDINGSERVICESACOUSTICS,SOUNDINSULATIONANDNOISECONTROL

9.4.1 SCOPE

This section covers requirements and guidelines regarding planning against noise, acceptable noiselevelsandtherequirementsforsoundinsulationinbuildingswithdifferentoccupancies.

9.4.2 DEFINITIONS

ForthepurposeofthisSection,thefollowingdefinitionsshallapply.

AmbientNoise The sound pressure levels associatedwith a given environment. Ambientnoiseisusuallyacompositeofsoundsfromnearandfarsourcesnoneofwhichareparticularlydominant.

AudibleFrequencyRangeTherangeofsoundfrequenciesnormallyheardbythehumanear.Theaudiblerangespansfrom20Hzto20000Hz.

AWeightedSoundPressure,PAValueofoverall soundpressure,measured inpascals (Pa),aftertheelectricalsignalderivedfromamicrophonehasbeenpassedthroughanAweightingnetwork.

NOTE The Aweighting network modifies the electrical response of a sound level meter withfrequencyinapproximatelythesamewayasthesensitivityofthehumanhearingsystem.

AWeightedSoundPressureLevel,LPAQuantityofAweightedsoundpressure,givenbythefollowingformulaindecibels(dBA):

LPA=10LOG10(pa/pO)2

Where

PA=istheAweightedsoundpressureinpascals(Pa):and

Po=isthereferencesoundpressure(20Pa).NOTEMeasurementsofAweighted soundpressure level canbemadewithameterand correlateroughlywithsubjectiveassessmentsofloudness,andareusuallymadetoassistinjudgingtheeffectsofnoise onpeople. The size ofAweighting in 1/3octave bands, is shown inAnnexA (seeA5). Anincreaseordecreaseinlevelof10dBAcorrespondsroughlytoadoublingorhalvingofloudness.

Background Noise The sound pressure levels in a given environment from all sourcesexcludingaspecificsoundsourcebeinginvestigatedormeasured.

BreakinUnwantedsoundtransmissionintoaductfromoutside.

3

BreakoutUnwantedsoundtransmissionfrominsideaducttotheoutside.

BroadbandNoiseSpectrumconsistingofa largenumberoffrequencycomponents,noneofwhichisindividuallydominant.

CrossTalkUnwantedsoundtransmissionbetweenoneroomandanotherroomorspaceviaaduct.

DecibelsTentimesthelogarithm(tothebaseoftheratiooftwomeansquarevaluesofsoundpressure,soundpowerorsoundintensity.TheabbreviationfordecibelsisdB.

EffectivePerceivedNoise Level inDecibel (EPNdB)Thenumber for rating thenoiseofanindividualaircraftflyingoverheadistheeffectiveperceivednoiselevelindecibels(EPNdB).Theeffectiveperceivednoisedecibelvalue takes intoaccount thesubjectivelyannoyingeffectsofthenoiseincludingpuretonesandduration.Inprinciple,itisakindoftimeintegratedloudnesslevel.

Equivalent Continuous AWeighted Sound Pressure Level, LAeg.T Value of the Aweightedsoundpressurelevelindecibels(dB)ofacontinuous,steadysound,thatwithinaspecifiedtimeinterval,T,hasthesamemeansquaredsoundpressureasthesoundunderconsiderationthatvarieswithtime,givenbytheformula:

LAeg.T=10log10( )

dtP tPT

T

O o

A2

21

Where

PA(t) = istheinstantaneousAweightedsoundpressureinpascals(Pa);and

Po = isthereferencesoundpressure(20Pa).NOTEEquivalentcontinuousAweightedsoundpressurelevelismainlyusedfortheassessmentofenvironmentalnoiseandoccupationalnoiseexposure.

Equivalent Sound Absorption Area of a Room A Hypothetical area of a totally absorbingsurfacewithoutdiffractioneffects,expressed insquaremetres (m2)which, if itwere theonlyabsorbing element in the room,would give the same reverberation time as the roomunderconsideration.

FaadeLevelSoundpressurelevelmeasured1mto2minfrontofthefaade.

NOTEFaadelevelmeasurementsofLPAareusually2dBto3dBhigherthancorrespondingfreefieldmeasurements.

FreeFieldLevelSoundpressurelevelmeasuredoutside,farawayfromreflectingsurfaces.

4

NOTE Measurementsmade 1.2m to 1.5m above the ground and at least 3.5m away from otherreflectingsurfacesareusually regardedasbeing freefieldmeasurements. Tominimize theeffectofreflectionsthemeasuringpositionshouldbeatleast3.5mtothesideofthereflectingsurface(thatis,not3.5m from the reflectingsurface inthedirectionof thesource). Estimatesofnoise fromaircraftoverheadusuallyincludeacorrectionofdBtoallowforreflectionfromtheground.

FrequencyThenumberofcyclicalvariationsperunittime.Frequencyisgenerallyexpressedincyclespersecond(cps)andisalsodenotedasHertz(Hz).

ImpactSoundPressureLevel,LiAveragesoundpressurelevelinaspecificfrequencybandinaroombelowafloor,whenitisexcitedbyastandardtappingmachine.

IndoorAmbientNoisePervasivenoise inagivensituationatagiventime,usuallycomposedofnoisefrommanysources,insideandoutsidethebuilding,butexcludingnoisefromactivitiesoftheoccupants.

InsertionLoss(LIL)

Insertion loss isgenerallydefinedas thedifference, indecibels,between two soundpressurelevels(orpowerlevelsorintensitylevels)whicharemeasuredatthesamepointinspacebeforeand after amuffler or any other noise control device is inserted between themeasurementpointandthenoisesource.

NoiseUnwantedsoundwhichmaybehazardoustohealth,interfereswithcommunicationsorisdisturbing.

NoiseExposureForecast(NEF)Thenoiseexposureforecastatanylocationisthesummationof thenoise levels inEPNdB fromallaircraft types,onall runways,suitablyweighted for thenumberofoperationsduringdaytimeandnighttime.

NoiseRating(NR)Graphicalmethodforratinganoisebycomparingthenoisespectrumwithafamilyofnoiseratingcurves.

NOTENoiseratingisdescribedinAnnexC.

NoiseReductionCoefficient(NRC)

Asingle figuredescriptorof thesoundabsorptionpropertyofamaterial. It is thearithmeticmeanofthesoundabsorptioncoefficientsat250,500,1000and2000Hzroundedofftothenearestmultipleof0.05.

Normalized ImpactSoundPressure Level, Ln Impact soundpressure levelnormalized forastandardabsorptionareainthereceivingroom.

NOTENormalizedimpactsoundpressurelevelisusuallyusedtocharacterizetheinsulationofafloorinalaboratoryagainstimpactsoundinastatedfrequencyband(seeAppendixB).

5

OctaveBandBandoffrequenciesinwhichtheupperlimitofthebandistwicethefrequencyofthelowerlimit.

Percentile Level, LAN,T Aweighted sound pressure level obtained using timeweighting F,whichisexceededforNpercentofaspecifiedtimeinterval.

Example:

LA90,lhistheAweightedlevelexceededfor90percentof1h.Percentilelevelsdeterminedoveracertaintimeintervalcannotaccuratelybeextrapolatedtoothertimeintervals.TimeweightingFor Scanbe selectedonmostmodernmeasuring instrumentsandused todetermine thespeed atwhich the instrument responds to changes in the amplitude of the signal. Timeweighting F is faster than Sand so itsusecan lead tohighervalueswhen rapidlychangingsignalsaremeasured.

PinkNoise Soundwith anuninterrupted frequency spectrum and apowerwhich is steadywithin frequencybandandproportional tocentre frequencybandandproportional tocentrefrequency.Anexampleisconstantpowerlevelperoctaveband.

PureToneAsoundemittedatasinglefrequency.

RatingLevel,LAr,TrEquivalentcontinuousAweightedsoundpressurelevelofthenoise,plusanyadjustmentforthecharacteristicfeaturesofthenoise.

NOTEThisdefinitionisusedforratingindustrialnoise,wherethenoiseisthespecificnoisefromthesourceunderinvestigation.

ReverberationTime,TTimethatwouldberequiredforthesoundpressureleveltodecreaseby60dBafterthesoundsourcehasstopped.

NOTEReverberationtimeisusuallymeasuredinoctaveorthirdoctavebands.Itisnotnecessarytomeasurethedecayoverthefull60dBrange.Thedecaymeasuredovertherange5dBto35dBbelowtheinitiallevelisdenotedbyT30,andovertherange5dBto25dBbelowtheinitiallevelbyT20.

Sound A vibrational disturbance, exciting bearing mechanisms, transmitted in predictablemannerdeterminedbythemediumthroughwhichitpropagates.Tobeaudiblethedisturbanceshallhavetofallwithinthefrequencyrangeof20Hzto20000Hz.

SoundExposureLevel,LAELevelofasound,of1sduration,thathasthesamesoundenergyastheactualnoiseeventconsidered.

Notes

1. TheLAEofadiscretenoiseeventisgivenbytheformula:

6

LAE=10log10( )

dtP tPt

t

t o

A

o

2

12

21

Where

PA(t) = istheinstantaneousAweightedsoundpressureinpascals(Pa);

t2t1 = isastatedtimeintervalinseconds(s)longenoughtoencompassallsignificantsoundenergyoftheevent;

Po = isthereferencesoundpressurelevel(20Pa);and to = isthereferencetimeinterval(1s). 2LAEisalsoknownasLAX(singleeventnoiseexposurelevel). SoundPowerTheacousticpowerofasoundsource,expressedinWatts.

SoundPowerLevel,LWTheacousticpowerradiatedfromagivensoundsourceasrelatedtoareferencepowerlevel(typically1012watts)andexpressedindecibelsas:

Lw=10log

1210W

Where

W = Acousticpowerinwatts.

Bydefinition,IWthereforecorrespondsto120dBforLw.

Sound Pressure, p Rootmeansquare value of the variation in air pressure measured inpascals(Pa),aboveandbelowatmosphericpressure,causedbythesound.

SoundPressureLevel,LpQuantityofsoundpressure,indecibels(dB),givenbytheformula:

Lp = 10log10(p/po)2

Where

P = istherootmeansquaresoundpressureinpascals(Pa);and

PO = isthereferencesoundpressure(20Pa).NOTEThe rangeof soundpressures forordinary sounds isverywide. Theuseofdecibelsgivesasmaller,moreconvenientrangeofnumbers.Forexample,soundpressurelevelsrangingfrom40dBto

7

94 dB correspond to sound pressures ranging from 0.002 Pa to 1 Pa. A doubling of sound energycorrespondstoanincreaseinlevelof3dB.

SoundReceiverOneormoreobservationpointsatwhich sound isevaluatedormeasured.Theeffectofsoundonanindividualreceiverisusuallyevaluatedbymeasurementsneartheearorclosetothebody.

SoundReductionIndex,RLaboratorymeasureofthesoundinsulatingpropertiesofamaterialorbuildingelementinastatedfrequencyband.

NOTEForfurtherinformationseeAnnexB.

Sound Source Equipmentorphenomenawhich generate sound. Sound room is the roomcontainingsoundsource.

Spectrum A quantity expressed as a function of frequency, such as sound pressure versusfrequencycurve.

Standardized ImpactSoundPressureLevel,LnT Impactsoundpressure levelnormalizedtoareverberationtimeinthereceivingroomof0.5s.

NOTE Standardized impact sound pressure level isused to characterize the insulation of floors inbuildingsagainstimpactsoundinastatedfrequencyband(seeAnnexB).

SpeechInterferenceLevel(SIL)Adescriptorforratingsteadynoiseaccordingto itsabilitytointerferewith conversationbetween twopeople. SIL is the arithmetic averageof the soundpressurelevelsinthethreeoctavebandswithcentrefrequenciesat500,1000and2000Hz.

Standardized LevelDifference,DnTDifference in sound levelbetweenapairof rooms, inastatedfrequencyband,normalizedtoareverberationtimeof0.5s.

NOTEStandardizedleveldifferencetakesaccountofallsoundtransmissionpathsbetweentherooms(seeAnnexB).

StructureBorneNoiseGenerationandpropagationoftimedependentmotionsandforcesinsolidmaterialswhichresultinunwantedradiatedsound.

TransientSoundSoundwhichisaudibleforalimitedperiodoftime,forexamplesoundfromoverflightofanairplane.

ThirdOctaveBandBandoffrequenciesinwhichtheupper limitofthebandis21/3timesthefrequencyofthelowerlimit.

Threshold of Hearing The lowest continuous sound pressure level which will create anauditorysensationfortheaveragehumanear. Anysoundbelowthese levelswillbe inaudibleandanysoundabovethethresholdwillvaryinloudnessdependentonintensity.

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Vibration Isolation Reduction of force or displacement transmitted by a vibratory source,oftenattainedbyuseofaresilientmount.

WavelengthThelengthinspaceofonecompletecycleofasoundwave.

= (Speedofsound)=(C) (frequency) (f)Weighted LevelDifference,Dw Singlenumberquantity that characterizesairborne soundinsulationbetweenroomsbutwhichisnotadjustedtoreferenceconditions.

NOTEWeightedleveldifferenceisusedtocharacterizetheinsulationbetweenroomsinabuildingastheyare:valuescannotnormallybecomparedwithmeasurementsmadeunderotherconditions(seegoodpractice[84(1)]].

Weighted Sound Reduction Index, RW Single number quantity which characterizes theairborne sound insulating properties of a material or building element over a range offrequencies.NOTE Theweighted sound reduction index is used to characterize the insulation of amaterial orproductthathasbeenmeasuredinalaboratory(seeAnnexB).WeightedStandardized ImpactSoundPressure Level,LnT,wSinglenumberquantityused tocharacterizetheimpactsoundinsulationoffloorsoverarangeoffrequencies.NOTE Weighted standardized impact sound pressure level is used to characterize the insulation offloorsinbuildings(seeAnnexB).WeightedStandardizedLevelDifference,Dn,TwSinglenumberquantity,whichcharacterizestheairbornesoundinsulationbetweenrooms.NOTEWeightedstandardizedleveldifferenceisusedtocharacterizetheinsulationbetweenroomsinabuilding(seeAnnexB).Weighted Normalised Impact sound Pressure Level, Ln.w Single number quantity used tocharacterizetheimpactsoundinsulationoffloorsoverarangeoffrequencies.

NOTEWeightednormalizedimpactsoundpressurelevelisusuallyusedtocharacterizetheinsulationoffloorstestedinalaboratory(seeAnnexB).

WhiteNoiseAnoisewhosespectrum(level)densityissubstantiallyindependentoffrequencyoveraspecifiedrangeandhasequalpowerforanyrangeoffrequenciesofconstantbandwidth.

9

9.4.3.0 PLANNINGANDDESIGNAGAINSTOUTDOORNOISE

9.4.3.1 General

Planning against noise should be an integral part of town and country planning proposals,ranging from regional proposals to detailed zoning, and threedimensional layouts and roaddesignwithinbuiltupareas.Noisenuisanceshouldbefullyrecognizedinzoningregulations.

9.4.3.1.1 Noise iseithergeneratedbytraffic(roadandrail)or itarisesfromzonesandbuildingswithinbuiltupareas(industry,commerce,officesandpublicbuildings).Forplanning,thenoisesurveyshouldexamineallthepossiblecausesofnoiseandconsiderthevariousfactorscausingactualnuisance.

9.4.3.1.2 Noisebynight,causingdisturbanceofsleep,ismoreofnuisancethannoisebyday.Forthisreason,housingcoloniesthatadjoinareaswithheavytrafficmovementduringthenightareliable to cause serious complaints. Also, the factories thatworkbynight are liable to causeseriouscomplaints ifhousingestatesadjoin them. Whileplanning,careshouldbe taken thathousing colonies are adequately setback from busy airports, state and national highways,factories,mainrailwaylinesandmarshallingyards.

9.4.3.1.3 Therearetwoaspectsofdefencebyplanning.Thefirstistoplansoastokeepthenoiseat a distance. Under this aspect comes the separation of housing from traffic noise byinterposing buffer zones, and the protection of schools and hospitals by green belts, publicgardens,etc. Thesecond istheprincipleofshadingorscreening. Thisconsistsofdeliberatelyinterposinga lessvulnerablebuilding toscreenamorevulnerableoneorbyprovidingasolidbarrier,suchasawall,betweenthesourceandthelocationtobeprotected.

9.4.3.2 TrafficNoiseLevels

9.4.3.2.1ForAirTraffic

Forguidance,approximatenoise levelsduetovarioustypesofaircrafts,measuredonground,whentheaircraftsflyoverheadataheightof450m,aregiveninTable1.

Table1 TypicalNoiseLevelsofSomeAircraftTypes

(Clause9.4.3.2.1)

(1)

TypeofAircraft

(2)

FlyoverNoiseLevelsat450mwithTakeoffThrust(EPNdB)

(3)i) Boeing737 107ii) Boeing747200 103iii) AirbusA300 101iv) ConcordeSST 114

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9.4.3.2.2 ForRailTraffic

NoiselevelsofsometypicalrailwaytrafficaregiveninTable2.

Table2 TypicalNoiseLevelsofRailwayTrains

(Clause9.4.3.2.2)

(1)

TypeofAircraft

(2)

FlyoverNoiseLevelsat450mwithTakeoffThrust(EPNdB)

(3)i) Steamtrain,60km/h 85ii) Dieseltrain,60km/h 83iii) Electrictrain,60km/h 77

9.4.3.2.3 ForRoadTraffic

The level of noise generated by road traffic depends upon such factors as the number ofvehicles passing per hour, the type of traffic, the preponderance of heavy vehicles, averagespeed, gradient and smoothness of traffic flow. The smoothness of traffic flow also affectsvariabilityofthenoiseandisgovernedbysuchthingsasroundaboutsandtrafficlights,andthevolume of traffic and pedestrian movement with their effects on stopping, starting andovertaking. The level of traffic noise fluctuates continuously and the way it does has aconsiderableeffecton thenuisance caused. Forassessing trafficnoise,noise ismeasured indB(A). Because of the fluctuating nature of traffic, noise levels due to different volumes oftrafficflowwithavaryingmixofvehiclesaregiveninTable3.

Table3TypicalNoiseLevelsDuetoFreeFlowingRoadTraffic

(Clause9.4.3.2.3)

No.

TypeofTraffic

L1030mfromEdgeofRoad,dB(A)

i) 5000vehiclesper18hourday(10percent

heavyvehicles),50kmph

65

ii) 10 000 vehicles per 18 hour day (20percentheavyvehicles),60kmph

70

iii) 10 000 vehicles per 18 hour day (40percentheavyvehicles),80kmph

75

iv) 20 000 vehicles per 18 hour day (40percentheavyvehicles),80kmph

77

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NOTEThevaluesareapplicabletofreeflowingtrafficwithouthonking.

9.4.3.3 OutdoorNoiseRegulations

Theoutdoornoiseregulationsinforcefromtimetotimeshallbecompliedwith(seealsoAnnexD).

9.4.3.4 PlanningandDesign

9.4.3.4.1 ForAirTraffic

a) FlyovernoiseFlyovernoise is thatwhichoccursunder flightpathsclose toairportsand is themost serious and common problem. As the aircraft passes overhead thenoiselevelatanyparticularlocationrisestoapeakandthendecreases.

b) Ground noise The noise emitted by an aircraft during ground operations is lessvariableindirectionthanflyovernoise,butisusuallyofalongerduration.

9.4.3.4.1.1 Aircraft noise may disturb sleep, rest and communication, and as such may beconsideredpotentiallyharmfultohealth.Itisimportantthatnonewdevelopmentiscarriedoutwithin areas where the expected noise levels will cause mental and physical fatigue orpermanent loss of hearing. In case development in such areas is essential, adequate soundinsulationshallbeprovidedforthebuilding.

9.4.3.4.1.2 As the problems caused by aircraft noise have become more acute, a number ofmethodshavebeendevised forevaluatingnoiseexposure in thevicinityofairports. Theyallcombinemanyfactorsintoasinglenumberevaluation.Acommonlyusedcriterionisthenoiseexposureforecast(NEF).TheNEF isusedprimarilytodevelopnoisecontoursforareasaroundairports.IthasbeenacceptedgenerallythatnoiseexposureforecastlevelsgreaterthanNEF40areunacceptabletopeoplewhilelevelslessthanNEF25arenormallyacceptable.

9.4.3.4.1.3 Whileitistheoreticallypossibletoprovidesufficientinsulationtoachieveanacceptableindoornoiseenvironment intheareaofveryhighoutdoornoise,there isa levelabovewhichaircraftnoiseseriouslyaffectslivingconditionsnomatterhowmuchsoundinsulationhasbeenappliedtothedwellingunit.ForthisreasonitisrecommendedthatnoresidentialdevelopmentbeallowedbeyondtheNEF35level.

9.4.3.4.1.4 Duringsummermonths,thewindowsarenormallykeptopenforadequateventilation.Inviewofthis,nomatterhowmuchsoundinsulationisprovidedforthebuildingstructure,thenoiselevelinsidetheroomcanneverbelessthan10dBbelowtheoutdoornoiselevel.Forverycritical buildings, such as buildings necessary formaintaining and supplementing the airportservices, and for commercial development, such as hotels, it is possible to provide sealedwindowsandtocentrallyairconditiontheentirebuilding.However,itisnotfeasibleformost

12

of the residentialdevelopments in the country. In such casesproper zoning regulationsandsittingofvulnerablebuildingsawayfromaircraftnoisereofvitalimportance.

9.4.3.4.2 RailTraffic

This is a very serious source of noise in builtup areas, both by day and by night. Railwaycuttingsreducethespreadofnoise,whereasembankmentsextendit.Theelevatedrailwayonviaductsorembankmentisverycommoninbuiltupareas.Theelevationincreasesexposuretonoisebutinadditiontheconstructionoftheviaductmayaffectthepropagationofnoise.Inthisrespectsolidembankmentsarepreferabletobuiltuparches,whichtendtoactassoundboxes.Worst of all are the steel bridges,which greatlymagnify the noise due to vibration. Uphillgradientsareanotherfeaturetendingtoincreasenoise,especiallyofheavygoodstrains.

9.4.3.4.2.1 Whereverpossible,noresidentialorpublicbuildingzoneshouldabutontorailwaylines,especially in themarshalling yardswhich are particularly objectionable because of the shrill,clangingandintermittentnoisetheygenerate,oftenatnight.Theappropriatezonesalongsiderailway linesare industrialandcommercialbuildingsotherthanofficebuildings. Wheretheseprecautionsarenotpracticableandhousinghastoabutontorailwaylines,everyattemptmaybemadetohouseasfewpeopleaspossibleinthevicinityoftherailwaylines.

9.4.3.4.2.2 Underground transportation system can be a major cause of disturbance for theneigbouring community. Very high noise levels are propagated to long distances by theundergroundhighspeedrailway,asaresultofwheelrailinteraction.Bothairbornenoiseandground or structureborne vibration are potential sources of complaints. Noise controlmeasures,therefore,needtobeconsideredforthefollowing:

a) Instation,wherehighnoiselevelsareproducedatthearrivalanddepartureoftrains;

b) Intunnels,duringhighspeedtrainmovement;

c) whereanundergroundrailtransitsystempassesclosetoexistingstructuresorhighrisebuildings adequate attention should alsobepaid to theproblemof ground vibrationtransmittedtothebuilding,andproperisolationshouldbeprovidedforcriticalareas;

d) Whereverelevatedrailwaytracksareprovided,adequatemeasuresshouldbetakentoavoidthespreadofnoiseinthesurroundingbuiltupareas;and

e) In transit cars,where sound insulation is of vital importance to provide comfortableconditionsforthecomments.

9.4.3.4.3 RoadTraffic

9.4.3.4.3.1 Convoysoflongdistanceheavytrucksatnightmovingpastthroughbuiltupareascauseserious noise complaints. On busy roads, the noise of continuous traffic may be a worsenuisancethanthatofrailways. At leastthesameprecautionsmay,therefore,betaken inthe

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planningofdwellingsinrelationtoarterialandtrunkroadsaswithrailways.Caremaybetakenthatlocalhousingroadsdonotprovideshortcutsforheavytraffictroughresidentialareas.Hillyroadspresenttheadditionalnoiseofgearchanging. Treeswithheavyfoliageplantedonbothsides of carriageway help slightly to muffle the noise, provided the foliage extends for aconsiderabledistance(30morabove).

9.4.3.4.3.2 Road traffic may give rise to serious nuisance particularly on busy thorough fares,betweencontinuoushighbuildingsinmainstreets,atthetrafficlights,nearbusstops,onsteepslopesandinparkingspacesandenclosedyards.

9.4.3.4.3.3 ForzoningandplanningnewbuildingsinurbanareasitisrecommendedthatexternalLA10 is limited to amaximum of 70 dB (A)when the dwellings are proposed to have sealedwindowsand60dB (A)whenthedwellingsareproposedtohaveopenwindows. Indeed it isdesirable to confine major new residential development to locations subject to LA10 levelssubstantiallylowerthanthosegivenabove.

Itisrecognized,however,thatwithinthelargeurbanareas,theuseofsiteswheretheexternalLA10isgreaterthan6070dB(a)cannotalwaysbeavoided.InthatcaseitissuggestedtoutilizesuchdesignsolutionsasbarrierblocksinordertoreduceexternalLA10noiselevelstoatleast6070dB(A)atanypoint1.0mfromanyinwardlookingfaade.Whentheorientationofsiteandthedensityofdevelopmentaresuchthatthiscannotbefullyachievedsomeformofdwellinginsulationwillhavetobeprovided. Itshouldbeappreciated thatwhereopenwindowsareamust,theoccupantswouldhavetoputupwithdiscomfortiftheaboveconditionsarenotmet.

9.4.3.4.3.4 Certain other methods can often be utilized to provide economical and effectiveprotectionfromnoise:

a) Methodsmaybeadopted to improve the smoothnessof flowand reducenumberofstoppingandstarting.Thisleadstoanimprovementevenifitleadstoincreasedflows.Flowlinkingoftrafficlights,forexample,mayreducenoisenuisance.

b) Useofroadspassingthroughresidentialareasmaybeprohibitedtoheavycommercialvehicles.Analternativewouldbetolimitusebycommercialvehiclestocertaintimesoftheday.

c) Useofhonkingmaybeprohibitednear sensitivebuildings, such ashospitals and thelike.

d) Barriersmaybeprovidedtoshieldsitesfromnoise.

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9.4.3.5 Zoning

The zoningof thedifferent cities shallbedoneby the townplanning authorities, taking intoaccount besides other aspects, the noise levels from different occupancies. Wherevernecessary,expertsinthefieldmaybeconsulted.

9.4.3.6 GreenBeltsandLandscaping

Whererelieffromnoiseistobeprovidebymeansofgreenbeltsthesemaybeofconsiderablewidthandbelandscaped.(Incaseofrailwaytracks,aminimumdistanceof50mto70mmaybeprovidedbetween thebuildingsand the tracks). Theextentof relief thatmaybederivedfrom theabovemaybeestimatedonlyafter consideringotherenvironmental factors. Onlythickbeltsofplanting(greaterthan30m)areofrealvalue.Strongleafytreesmaybeplantedtoactasnoisebaffles.Shrubsorcreepersmayalsobeplantedforadditionalprotectionbetweentree trunks; artificialmounds and banks should be formedwhere practicable. As little hardpavingandasmuchgrassaspossiblemaybeused. Thecreationofgreenbelt isparticularlyadvisableon theperimeterofaerodromes,along railway lines andarterial roads, throughorpastbuiltupareasandadjoiningnoisyindustrialzones.

9.4.3.7 HighwayNoiseBarriers

Barriersareoften themosteffectivemeansofreducing trafficnoisearoundresidentialareas.Theyhavethegreatadvantagethattheygenerallyprotectmostorallofthesites.Innearlyallsituations,awelldesignedbarrierofevenamodestheight(say3m)canatleastensurethatallareasofopenspacearefreefromexcessivenoiselevels.

Therearetwotypesofbarriersthatcanbebuilttoprotectsites;onewhicharebuiltsolelyforthepurposeofreducingnoiseandtwo,whichformpartofthebuildingcomplex(barrierblocks).Freestandingwallsandartificialmoundsaretypicalexamplesofthefirsttypewhilesingleandmultistoreyeddwellingsand/orgaragesarethemostcommonformofthesecond.

Ofthetwotypes,barrierblocksaremorewidelyusedbecausetheyarecheaperandalsotendtoformamoreeffectivebarrieroverallbecauseoftheirgreaterheightandwidth.Barrierwallsormoundsaremorelimitedintheireffectthanbarrierblocksfortheyprotectlittlemorethantheareaofthesiteclosetogroundlevelessentiallybecauseofthelackofheight,ascontinuouswallsmuchhigherthan3mareoftendifficulttoconstruct.

9.4.3.8 SpecialProblemsRequiringExpertAdvice

The purpose of noise control is to ensure that people are neither harmed nor disturbed bynoise. Inadditiontoprovisionsgiven inthisSection,specialadvicemayberequiredformorecomplexsituations,suchasthoselistedinAnnexE.

15

9.4.4.0 PLANNINGANDDESIGNAGAINSTINDOORNOISE

9.4.4.1 Acceptableindoornoiselevelsinbuildings

ThegenerallyacceptablenoiselevelsinsidebuildingsaregiveninTable4.

Table4 Acceptableindoornoiselevelsforvariousbuildings

(Clause9.4.4.1)

No.

Location

NoiseLeveldB(A)

i)ii)

AuditoriaandconcerthallsRadioandTVstudios

20252025

iii)iv)v)

CinemasMusicroomsHospitalsandcinematheatres

253025303540

vi)vii)

Apartments,hotelsandhomesConferencerooms,smallofficesandlibraries

35403540

viii)ix)x)

CourtroomsandclassroomsLargepublicoffices,banksandstoresRestaurants

404545505055

9.4.4.2 VulnerableBuildings

Somebuildingsorpartsofbuildingsareespeciallyvulnerable tonoise, forexample,recordingand radio studios, hospitals and research laboratories. These should not be sited near loudnoisesources.Mostvulnerablebuildingscontainsomeareaswhicharethemselvesnoisyandinsuchbuildings the lessvulnerableelements shouldbeplanned toactasnoisebuffers. Mostnoisybuildingsalso containquiteaccommodation,whichequallymaybeplanned toactasabufferbetweenthenoisypartofthebuildingandadjoiningvulnerablebuildings.

9.4.4.3 The details of site and internal planning and insulation requirements are covered underindividualoccupancies(5to12)asapplicabletotherespectivecharacterandsourcesofnoiseindifferentbuildings.

9.4.4.4 SoundInsulationofNonIndustrialBuildingsbyConstructionMeasures

Thedesired(acceptable)noiselevelsandtherecommendinsulationvaluesforthevariousareasmaybe achievedbyproviding sound insulation treatmentsby constructionalmeasures. ThedetailsofthesamearegiveninAnnexF.TherecommendationsgiveninAnnexFareapplicabletononindustrialbuildingslikeresidences,educationalbuildings,hospitalsandofficebuildings.

16

9.4.4.5 Specialproblemsrequiringexpertadvice(see9.4.3.8andAppendixE)

9.4.5.0 RESIDENTIALBUILDINGS

9.4.5.1 Sourcesofnoisenuisance

9.4.5.1.1 Outdoornoise

The main sources of outdoor noise in residential areas are traffic (aeroplanes, railways,roadways,)childrenplaying,hawkers,servicesdeliveries,roadrepairsblaringloudspeakersandvarioustypesofmovingmachineryintheneighbourhoodandbuildingoperations.

9.4.5.1.2 Indoornoise

9.4.5.1.2.1 Asfarasindoornoisesareconcerned,conversationoftheoccupants,footsteps,bangingofdoors, shiftingof the furniture,operationof thecisternandwatercloset,playingof radio,television,musicsystem,coolingandventilationmachinery,etc.contributemostof thenoiseemanatingfromanadjacentroomoranadjacentbuilding.Noiseconditionsvaryfromtimetotime and noise which may not be objectionable during the day may assume annoyingproportionsinthesilenceofthenightwhenquietconditionsareessential.

9.4.5.1.2.2 Inthecaseofflatsthemainsourcesofnoisearefromotherflatsandfromstairs, liftsandaccessbalconies. Plumbingnoise isanother cause. In semidetachedbuildings,outdoornoisesfromstreetsarenoticedmorethanindoornoisesfromneighbours.

9.4.5.2 Recommendations

9.4.5.2.1 SitePlanning

Themostdesirablemethod isto locatetheresidentialbuildings inaquietareaawayfromthenoisysourcesliketheindustrialareas,railtracks,aerodromes,roadscarryingheavytraffic,etc.

9.4.5.2.1.1 To minimize ground reflection, the dwellings should be surrounded by the maximumamountofplanting and grassed areasand theminimum amountofhard surfacing. Thisappliesparticularlytohighdensityareas.Whereformaintenancereasonsalargeamountofhardpavingisnecessary,itshouldbebrokenupbyareasofplantingandgrassing.Narrowhardpavedcourtsshouldbeavoidedbetweenadjacenttallbuildings.

9.4.5.2.1.2 Roadswithinaresidentialareashouldbekepttoaminimumbothinwidthandlength,and

should be designed to discourage speeding. Areawise planning,with zones fromwhichvehiculartrafficisaltogetherexcludedwillgreatlyhelptoreducenoise.Roadswiththroughtraffic should be excluded from residential areas, butwhere sites have to be developedadjacent to existingmajor roads the same principles should be observed in the siting ofblocksaswithrailwaylinesascoveredunder9.4.3.4.2.1.

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9.4.5.2.1.3 Playareasforolderchildrenshouldbesitedasfarawayfromdwellingsaspossible.Specialcareshouldbetakenwitholdpeoplesdwellings. Theyshouldnotbeplaced immediatelyadjacent to serviceentries,play spaces,or toanyentranceswhere childrenmay tend tocongregate.

9.4.5.2.2 InternalPlanning

Theorientationofbuildinginalocalityshouldbeplannedinsuchawayastoreducethenoisedisturbance from neighbourhood areas. The noncritical areas, such as corridors, kitchens,bathrooms,elevatorsandservicespacesmaybelocatedonthenoisysideandthecriticalareas,suchasbedroomsandlivingspace,onthequiteside.

9.4.5.2.2.1 WindowanddoorsWindowsanddoors shouldbekeptaway from thenoisy sideof thebuildingasgivenbelow,wheneverpossible:

a) whenwindowsofabuilding,particularlythoseofbedroomsinapartmentsorflats,faceroadscarryingheavytrafficorothernoiseswheretheexternalnoise isoftheorderof80to90dB(A),thebuildingshouldbelocatedatadistanceofabout30mfromtheroad,butadistanceof45mormore,wherepossible, shouldbeaimedat forgreater relieffromnoise.

b) Whenthewindowsareatrightanglestothedirectionoftheabovetypeofnoise,thedistancefromtheroadshouldbearrangedtobeabout15to25m;and

c) Incaseanotherbuilding,boundarywallortreesandplantationsintervenebetweenthe

roadtrafficandthehouse/flatfurthernoisereductionisachievedandinsuchcasestheabovedistancesmaybereducedsuitably.

9.4.5.2.2.2 Layoutplans

Itisdesirablethatroomsadjoiningpartywallsandabove/belowpartyfloorsshouldbeofsimilaruse.Bythismeans,bedroomsarenotexposedtonoisefromadjoininglivingrooms,andthereislessriskofdisturbanceofsleep.

Insemidetachedhouses,thestaircase,hallandkitchenshouldadjoineachotheroneachsideofthepartywall,thusprovidingasoundbafflebetweenroomsrequiringquietconditions.

Bedrooms shouldnotbe planned alongside accessbalconies, andpreferably notunderneaththem.Wheretheapproachisbyaninternalcorridor,asoundbafflemayusefullybeprovidebyarranging internal passages and bathrooms between the corridor and the living room orbedrooms.

Waterclosetsshouldnotbeplannedoverlivingroomsandbedrooms,whetherwithinthesamedwellingoroverotherdwellings. Soilpipesshouldnotbecarried inductswhichadjoin living

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roomsorbedroomsunlessthesizeoftheductnexttotheseroomsisasolidwallcontainingnoinspectionopenings.Refusechutesshouldnotbeplannednexttolivingroomsorbedrooms.

9.4.5.2.3 SoundInsulation

9.4.5.2.3.1 Reductionofairbornenoise

Theweightedsoundreductionindex,Rw,ofpartitionsbetweenindividualroomsorapartmentsofabuildingunitshallbeasgiveninTable5.Thesevaluesmay,however,besuitablyincreased,whererequired,forcriticalareas.

Table5Soundinsulationbetweenindividualrooms(AirBorne)

(Clause9.4.5.2.3.1)

No.

Location

Rw,dB

i)

(ii)

Between the living room in one house orflat and the living room and bedrooms inanotherElsewherebetweenhousesorflats

50

45

iii)

Betweenoneroomandanotherinthesamehouseorflat

35

Notes

1 Wherecommunicatingdoorsareprovided,alldoorsshouldbesodesignedastoproviderecommendedinsulationbetweentherooms.

2 Therearecaseswhenasetofhousesorflatshavetobebuiltforthepeoplewhoworkatnightandsleepduringtheday. Itisdesirabletoconsiderthedesignofatleastonesuchroomineachofthehousesorflatswhichwillprovideaninsulationofabout45dBinthatroom.

3 Theinsulationvaluesreferredtoareapplicablewithdoorsandwindowsshut.

9.4.5.2.3.2 Suppressionofnoiseatthesourceitself

All itemsofequipment thatarepotentiallynoisy shouldbe selectedwith care. Waterclosetcisterns shouldnotbe fixedonpartitionsnext tobedroomsor living rooms. Plumbingpipesshouldbe isolated from thestructures. Liftmotorsshouldbemountedon resilientsupports.

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Access doors from machine rooms to internal staircases should be well fitted and of solidconstruction. Special noise controlmeasuresmay be required for electrical andmechanicalservicessuchasdieselgenerators,outdoorairconditioningunits,coolingtowers,etc.

9.4.5.2.3.3 Reductionofairbornenoisetransmittedthroughthestructure

Reductionofairbornenoiserequirestheuseofrigidandmassivewallswithoutanyopenings.Openings are themajor cause of penetration of noise through a barrier. While designing itshouldbeborne inmindthatallcomponentsshouldprovideasoundtransmissioncompatiblewiththatoftherestofthebarriersothatanequivalentamountofsoundenergyistransmittedthrougheachportionofthebarrier.

Ventilating ducts or air transfer openings where provided should be designed to minimizetransmissionofnoise. For thispurpose, some soundattenuatingdevicesmaybe installed intheseopenings.

Allpartitionsshouldbesealedeffectivelywheretheybuttagainsttherestofthestructure.Alldoors andwindows shouldbeproperly gasketedwhere ahigh degreeof sound insulation isdesired.

9.4.5.2.3.4 Reductionofstructurebornenoise

Thisrequirestheuseofdiscontinuousornonhomogeneousmaterialsintheconstructionofthestructure.

9.4.5.2.3.5 Reductionofimpactnoise

Thefloorofaroomimmediatelyabovethebedroomorlivingroomshallprovideimpactsoundpressure level (LnTw)notgreater than60dB. Forexample,150mm thickconcrete floorwith(12mm)thickcarpetcoveringwouldsatisfythisrequirement.

9.4.5.2.3.6 Mainstaircasesinblocksofflatsareoftenhighlyreverberant.Someofthesurfacesatleast(for example, the soffitsof stairs and landings) shouldbe finishedwith sound absorbentmaterialswhereverrequired.

9.4.6 EDUCATIONALBUILDINGS

9.4.6.1Sourcesofnoisenuisance9.4.6.1.1OutdoorNoise

Theoutdoorsourcesofnoiseproducedonschoolpremises,whichcausedisturbanceswithintheschool, includethenoisearisingfromplayground,playingfieldsandopenairswimmingpools.Though playgrounds are used mainly during break periods, they are also used for games,physicaleducationandattimeswhenteachingisinprogressintheadjoiningclassrooms.

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9.4.6.1.2 Indoornoise

Indoorsourcesofnoiseareasfollows:

a) Singing,instrumentalandreproducedmusicwhichmaytakeplaceinclassroomsandindinning and assembly halls particularly in primary schools. In secondary schools,specializedmusicroomsaregenerallyprovided:

b) Themovementofchairs,desksandtablesattheendofoneperiodmaydisturbaclassengagedinalessoninaroombelow;

c) Theshuttingandopeningsofdoorsandwindowswhichmayoccuratanytimeduringteachingperiods;

d) Audiovisualpresentationsinclassrooms;e) Woodandmetalworkshops,machine shops (engineering laboratories), typing rooms,

etc.whichproducecontinuousorintermittentsoundofconsiderableloudness;f) Practicalworkcarriedoutingeneralteachingareas;g) Gymnasiaandswimmingpools;h) Schoolkitchensanddiningspaceswherefoodpreparationandthehandlingofcrockery

andutensilspersistforthegreaterpartoftheschoolday;corridorsandothercirculationspaces;and

i) Plumbingandmechanicalservices.

9.4.6.2 Recommendations9.4.6.2.1 Siteplanning

Whereoutdoornoisenuisance exists from local industry,busy roads, railway, airfields, sportgroundsorothersourcesbeyondthecontroloftheschoolauthority,schoolbuildingsshouldbesitedasfaraspossiblefromthesourcesofnoise.

9.4.6.2.1.1 Roomsshouldbeplannedinamannersothattheminimumamountofglazingisplacedon

thesidefacingtheexternalnoise.

9.4.6.2.1.2 Noisesarisingfromtheactivitiesofaschoolandfromtheuseofthebuildingsafterschoolhoursmay contribute a nuisance to occupants of surrounding property, therefore, it isdesirable toplaceplaygrounds,workshops, swimmingpools,music rooms,assemblyhallsandgymnasiaasfarawayaspossiblefrombuildingswhichrequireaquiteenvironment.

9.4.6.2.2 Internalplanning

Thefollowingprinciplesshouldbeobservedinthedetailedplanningofeducationalbuildings:a) GroupingNoisy roomsshouldbeseparated fromquiteones, ifpossible. Ingeneral, it is

desirablethatroomsshouldbegroupedtogetherinaccordancewiththeclassificationgivenin9.4.6.2.4.1.

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b) WindowsandventilatorsWindowsofnoisyandquietroomsshouldnotopentothesamecourtyardorbeneartooneanother.Rooflightsandventilatorsovernoisyroomsshouldbeavoided,iftheyarelikelytobeasourceofnuisancetoadjacentupperfloors.

c) Doors Swing doors into rooms should only be used where no problem of sound

transmission exists. Reduction of insulation between rooms and corridors due to doorsmustbeborneinmind.Thetypeandmethodoffittingofdoorsisimportantandnecessarycareshallbepaidinthisrespect.

d) Slidingpartitionsshouldonlybeusedwhereessential.e) OpeningplanningandcirculationareasWhereopenplanning isused topermitspaces,

suchasassemblyhalls,diningroomsorentrancehallstobeused inassociationwitheachotheror forcirculation, thedegreeofdisturbancecausedby interferingnoise to teachingareasneedscarefulconsideration; traffic throughsuchareasshouldbestrictlycontrolled;fulluseshouldbemadeofsoundabsorbenttreatmentstoreducethespreadofnoisefromonespacetoanother(see9.4.6.2.3).

Ifroomshave largeglazedpanelsorventilationopenings facingdirectlyonthecirculationareas, human traffic passing by the rooms should be controlled. Preferably baffledventilation systemordoublewindows shouldbe used. (Fanlightsoverdoors shouldbefixedandglazed).

f) FurnitureInalleducationalbuildings,regardlessofthecharacterofthefloorfinish,rubberbuffersshouldbefittedtothelegsofchairsandtables.

9.4.6.2.3 Noisereductionwithinrooms

Sound absorbentmaterials play a useful part in reducing the builtup or airborne noise atsource. In rooms, such as, classrooms, assembly halls and music rooms, a fairly shortreverberationtimeunderoccupiedconditionsisoneoftherequirementsoftheacousticdesign.Themaximumreverberationtimespermissibleforthispurposeareusuallyshortenoughtogiveadequatenoisecontrolbut inaddition, the reverberation timeshouldnotbeexcessiveunderemptyconditions,becausenoisemayoccur in theseroomswithvery fewoccupants. Table6gives the reverberation timesoftenarranged inoccupied rooms foracoustic reasonsand themaximumtimesrecommendedintheemptyroomsfornoisereduction;thetimesgivenareforafrequencyof500Hz,buttheyshouldnotbegreatlyexceededatanyfrequency.Whenroomsareusedforavarietyofpurposes,thereverberationperiodappropriatetothemajoruseshouldbeadopted.

9.4.6.2.3.1 Specialattentionshouldbegiventonoisereductioninschoolsforthedeafandschoolsfor

the blind. Deaf children are taught by means of hearing aids which cannot be usedsatisfactorily in high noise levels or in reverberant conditions. Blind children depend ongoodhearingforunderstandingspeechandfordetectingchangesinenvironment.Inboth

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thesetypesofschools,noiselevelsshouldbekeptlowandreverberationtimesshort.Asanexample, the reverberation times inempty classrooms shouldnotexceedone second inschoolsfortheblindor0.5secondinschoolsforthedeaf.

Table6Reverberationtimesinschools

(Clause9.4.6.2.3)

Room

ReverberationTime,sUsualforAcousticReasons

(Full)

Maximum1) forNoiseControl

(Empty)

i) Assemblyhalls 1.0 1.25accordingtosize 1.52.5accordingtovolumeofhall

ii) Musicteachingrooms 0.75 1.25 1.5

iii) Gymnasiaandindoorswimming pools 1.5

iv) Diningrooms 1.25

Classrooms 0.75 1.25

v) Headmastersroomandstaffrooms 0.5 1.00 1.0

1)Shorterreverberationtimesaredesirablefornoisecontrolwheneverpossible9.4.6.2.4 SoundInsulation9.4.6.2.4.1 AirborneNoise

Forpurposesofsoundinsulation,roomsineducationalbuildingsmaybeclassifiedasfollows:

ClassA NoiseProducing

WorkshopsKitchensDiningroomsGymnasiumsIndoorswimmingpoolsAssemblyhalls

ClassB Producingbutneedingquietattimes

LecturehallsMusicroomsTypingroomsGeneralclassroomsPracticalrooms

ClassC AverageLaboratoriesOffices

ClassD Roomsneedingquiet LibrariesStudies

ClassE RoomsneedingprivacyMedicalroomsStaffrooms

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9.4.6.2.4.2 Therecommendedminimumsoundreduction(Dw)betweenroomsofthesameclass isasfollows:

ClassA 25dB

ClassCorD 35dB

ClassBorE 45dB9.4.6.2.4.3 Where a room is likely to have a dual use, for example, a dining room to be used as a

classroom,thehighersoundinsulationvalueshouldbeused.

9.4.6.2.4.4 Therecommendedminimumsoundreduction(Dw)betweenroomsindifferentclassesis45dBsubjecttothefollowing:

a) Inschoolsor instituteswithatechnicalbiaswherenoisyactivities,suchassheetmetal

work,plumbingandwoodwork,are likelytobepracticedextensively innormalhours,categoryrequiringmorethan45Bisolation(Dw)formroomsofanyotherclass.

b) Assemblyhallsandmusic roomsare specialcases in that,aswellasproducingnoise,theyalsorequireprotectionfromitandmayneedmorethan45dBisolation(Dw)fromroomsinClassA,ifthelatterareverynoisy.

c) Circulationspacesmayvaryfromalongandfrequentedcorridortoasmallprivatelobbyand it is therefore difficult to give precise recommendations to cover them. ForpartitionsbetweenroomsinClassCandmostcorridors,aRwof35dBforthepartitionitselfisadequate.Forpartitionsbetweenroomsinotherclassesandcorridors,moreorlessinsulationmaybenecessary,dependinguponthespecificusage.

d) Theproblemofnoiseincirculationareasisasarulegreatlymitigatedinschoolsbythe

fact that classes usually change rooms together at regular times. In colleges andevening institutes, however, this is much less true and in such buildings particularattentionshouldbepaidtoinsulationbetweenroomsandcorridors.

9.4.6.2.4.5 Openplanschools

A new concept in school planning is the use of a large teaching area with simultaneousinstructions imparted to several groupsof students. Theseopenplan teaching areasoffer adifferent setofproblems. Becauseof the limitations inachievingagreatdealofattenuationacrossthespaceandrelateddifficultiesinnoisecontrolandspeechinterference,lecturingtoalargenumberof students isnotpossiblewithout interferingwithneighbouringgroups. Theshapeofsuchspacesmaybeaspossiblewithawidthtoheightratioof5:1orgreater.In addition, specialmeasures are required to be introduced to reduce the level of intrudingspeech to an acceptable value so that the various teaching groups are not disturbed andadequateprivacyismaintained.Judiciouspositioningofpartialheightbarriers1.8mto2.1minheightcan improve thesoundattenuationbetween teachinggroupsand theuseof reflectivescreenscanreinforcethespeechlocallywithoutreflectingittounwantedareas.

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9.4.6.2.4.6 Impactnoise

In thecaseofschools, theconcrete floorof the room immediatelyabove the teaching roomsshall provide an impact sound pressure level, Ln,Tw not greater than 70 dB. For example, acoveringof6mmlinoleumorcorktilesonconcretefloor(holloworsolid)weighingnotlessthan220kg/m2willusuallymeettheaboverequirement.

9.4.7 HOSPITALBUILDINGS9.4.7.1 General

Problemsofnoisecontrolvaryfromhospitaltohospitalbuttheprinciplesoutlinebelowapplytoalltypes.Aquietenvironmentinhospitalsisdesirableforpatientswhoareacutelyill.Staffrequiresquietconditionsforconsultationsandexaminationsandalsointheirlivingandsleepingquarters. Therehavebeen rapid rises innoise levels inhospitalsdue to thehigher levelsofoutdoor noise, increasing use ofmechanical andmobile equipment (some ofwhich is nowbrought much nearer to the patient in order to facilitate nursing procedure) and theintroductionof loudspeaker,radio,televisionandcallsystems. Noisecontrol inthehospital ismademuchmoredifficultby the extensiveuseofhardwashable surfaceswhich reflect andintensify thenoise. Inmosthospitals,windows to theopenairand fanlights tocorridorsareusually open for the purpose of ventilation, admitting noise from outside and allowing it tospreadthroughthebuilding.

9.4.7.2 SourcesofNoiseNuisance9.4.7.2.1 OutdoorNoise

Thismaybeclassifiedintotwomaincategories:a) Noise from sources outside the hospital premises, for example, traffic and industrial

noises;andb) Noise from sourcesoutside thebuildingbutusuallywithin thecontrolof thehospital

authority, for example, ambulances,motorcars and service vehicles, fuel and storesdeliveries,laundries,refusecollection,trucksandtrolleys.

9.4.7.2.2 IndoorNoise

A hospital is a complex building with many services and the numerous internal sources ofstructureborneandairbornenoisesaregroupedintothreemaincategories:a) Noise consequent upon hospital routines. This category includes sources which

transmitnoisethroughbothstructureborneandairbornepaths,manyofwhichmaybequiteneartopatientsparticularlythoseinwards,suchasthefollowing:

1) Wheeledtrolleysofvariouskind,forfoodandmedicalsupplies;2) Sterilizingequipment;3) Sluiceroomequipmentincludingbedpanwashers;

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4) Wardkitchenequipment;5) Footsteps;6) Doorsbanging;7) Thehandlingofmetalorglassequipment;8) Noisescausedduringmaintenanceandoverhaulofengineeringservices;and9) Vacuumcleaners,mechanicalpolishers,etc.

b) Loudspeaker,radioortelevision,audiblecallsystem,telephonebellsandbuzzers,and

otherairbornenoises,suchasloudconversation;andc) Noises from fixed or mobile equipment and services not directly concerned with

hospitalroutines.Theseincludeallthefixedservicesasgivenbelow:

1) plumbingandsanitaryfittings;2) steamhotandcoldwaterandcentralheatingpipes;3) ventilationshaftsandducts;4) fans5) boilers;6) pumps;7) aircompressors;8) pneumatictubes;9) electricalandmechanicalmotorsandequipment;10) lifts;11) laundryequipment;and12) mainkitchenequipment(refrigerators,mixers,steamboilers,etc).

9.4.7.3 Recommendations9.4.7.3.1 Siteplanning

Hospitalsiteswiththeirhighdegreeofsensitivitytooutsidenoiseshouldbeasfarawayfromoutside sources as may be compatible with other considerations, such as accessibility andavailabilityofservices. Thebuildingshouldbesoarrangedonthesitethatsensitiveareas likewards,consultingandtreatmentrooms,operatingtheatresandstaffbedroomsareplacedawayfromoutdoor sourcesof noise, ifpossible,with theirwindows overlooking areasof acousticshadow.

9.4.7.3.2 DetailedPlanning

Thereisaverylargenumberofunitsandroomclassificationinhospitaldesignandinplanningtheunits in relation to eachother and to the common services (such as Xraydepartments,operating theatre suits andmain kitchens), noise reduction in the sensitive areas should beweighed carefully against other design factors. Special care in overall planning and internalplanning against noise is required in the planning within the building of units which arethemselves potential noise sources, for example, childrens wards and outpatientsdepartments,partsofwhichrequireprotectionagainstnoise.

9.4.7.3.2.1 Unloadingbays,refusedisposalareas,boilerhouses,workshopsandlaundriesareexamples

ofserviceunitswhichshouldbeasfarfromsensitiveareasaspossible.

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9.4.7.3.2.2 The kitchen is a constant sourceofboth airborne and structurebornenoise and shouldpreferablybeinaseparatebuildingawayfromorscreenedfromthesensitiveareas.Ifthisisnotpossibleandthemainkitchensmustformpartofamultistoreybuilding,noisecontroliseasieriftheyareplacedbelowandnotabovethewardsandothersensitiveroomssoasto facilitate the insulation of the equipment and machinery in order to reduce thetransmissionofstructurebornenoisetoaminimum.

9.4.7.3.2.3 Inwardunits,thekitchens,sluicerooms,utilityrooms,sterilizingroomsandotherancillary

rooms,needtobeplacedquiteneartothebeds iftheyaretofulfilltheirpurposes,whichareallsourcesofnoise.Someformofnoisebafflingbetweenopenwardsandroomsofthiskinwillbeneeded.

9.4.7.3.3 ReductionofNoiseatService

Inviewof thedifficultyof suppressingnoise inhospitalbuildings, it is important toeliminatenoiseatitssourcewhereverpossible.

9.4.7.3.3.1 Useofresilientmaterial

Matsofrubberorotherresilientmaterialondrainingboardsandrubbershodequipmentwillgreatlyreducenoisefromutilityrooms,sluiceroomsandwardkitchens.Theuseofplasticsorother resilientmaterials for sinks,drainingboards,utensils andbowlswould also reduce thenoise. Many itemsofequipmentespeciallymobileequipment,suchastrolleysandbeds,maybesilencedbymeansofrubbertyredwheelsandrubberbumperandtheprovisionofresilientfloorfinishes(see9.4.7.3.4.1).Thelatteralsoreducesfootstepnoise.Silenttypecurtainrails,ringsandrunnersshouldbeused.Liftgatesanddoorsshouldbefittedwithbuffersandsilentclosinggear. Fansandothermachineryshouldbemountedonsuitableresilientmountingstopreventthespreadofnoisethroughthestructure.

9.4.7.3.3.2 Othermeasures

Noise fromwater or heating pipesmay be reduced by installing systemswhich operate atcomparativelylowpressureandvelocities.Silencingpipesandspeciallydesignedflushingactionreduce water closet noise at source and make structural measures easier to apply. Theventilationsystemshouldbedesignedsoasnottocreateanoiseproblem.Silentclosersshouldbefittedtodoors.

9.4.7.3.4 Reductionofnoisebystructuralmeans9.4.7.3.4.1 Insulation

Sincethevariousdepartmentsorunitsmaybeplannedinmanyways,onlygeneralguidanceontheinsulationvaluesforwallsandpartitionsisgivenasbelow:a) ItisrecommendedthatwallsorpartitionsbetweenroomsshouldnormallyhaveaRwof

atleast40dB.HighervaluesofRwofatleast45dBarenecessarywhereanoisyroomisadjacent toone requiringquietconditions. Doorsshouldbesolidwithclose fitting intheframes.

b) There is little insulation value indouble swingdoors andwhere these are fitted in anoisyroom theopeningshouldbeplannedso that it isscreened fromareasrequiring

27

quietbyabaffle lobby linedwithabsorbentmaterial. Veryhigh insulationvaluesmaybenecessaryinspecialcasesandexceptionalmeasuresmayberequired.

c) Solid floors with floating finishes and resilient surfaces are necessary particularlybetweenwardsandotherpartsof thebuilding. Ordinary timberboardon joist floorsshouldneverbeused.

d) Conduits,ventilationducts,chases,etc. shouldbeconstructed soasnot to formeasy

bypass for disseminating noise about the building, and should be provided withsufficient sound insulation. Pipeducts shouldbe completely sealed around thepipeswheretheypassthroughwallsorfloors.Ductscarryingwasteorwaterpipesshouldbelinedwith sound insulatingmaterial topreventnoise from thepipespassing throughductwallsintotheroomsthroughwhichtheypass.

9.4.7.3.4.2 Absorption

Mostsurfaces inhospitalsshouldbeeasilycleanable,soastopreventthebuildupofbacteriawhichmaycausecrossinfection.Manysoundabsorbentmaterialsofasoftnatureanddifficulttocleanareunsuitable foruse insomehospitalareasand losemuchof theireffectiveness, ifpaintedforhygienicreasons.Someporousmaterialswithverythinnonporouscoverings(likemineralwoolcoveredwiththinplastic sheets)havegood soundabsorptionandwhencoveredwithaperforated sheetmetalfacingcanbeusedinmostareasrequiringawashableacousticaltreatment.Innoisyareas,suchascorridorsandwaitingrooms,however,awiderchoiceofabsorbentsisavailable.Intheward,bedcurtains,windowcurtainetc,addtotheabsorbentpropertiesoftheroomandhelpreducereverberationinotherwisehardsurfacedsurroundings.

9.4.7.3.5 Sensitiveareassuchasoperationtheatres,Doctorsconsultationrooms,intensivecareunits

(ICU) require special consideration against noise control. Apart from outdoor noise, acommon problem is the transmission of sound between the consulting room and thewaitingroom.Toensuresilence,asoundisolationDwof45B(A),betweentheroomsshallbeprovided.Ifthedoorsaredirectlyconnectedbyasinglecommunicatingdooritwillnotbe possible to achieve these values of isolation Dw. To obtain 4045 dB(A) insulationbetween communicating rooms, it isnecessary toprovide twodoors separatedbyanairgap,suchaslobbyorcorridor.

9.4.8 OFFICEBUILDINGS9.4.8.1 General

Modernofficebuildings areoftennoisier thanolderbuildingsdue to theuseof thinner andmorerigidformsofconstruction,harderfinishes,moreausterefurnishingsanduseofbusinessmachines.

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9.4.8.2 Sourceofnoisenuisance9.4.8.2.1 Indoornoise

Mainsourcesofindoornoiseincludethefollowing:a) Officemachines,suchastypewriters,andprinters;b) Telephoneconversation;c) Noisefromthepublicadmittedtothebuilding;d) Footsteps,voicesandslammingofdoorsincirculationspaces,liftdoorsandgates;e) Soundreproductioninstafftrainingrooms,conferenceroomsandrecreationrooms,etc;f) Handingofcrockeryandutensilsincanteensandkitchens;andg) HVACandliftmachinery.

9.4.8.3 Recommendations9.4.8.3.1 Siteplanning

Roomsdemandingquietconditionsshouldbeplacedonthequietsideofthesite.Evenonquietthoroughfares,theseroomsshouldalsonotbeplannedatstreetlevel.Theyshouldalsonotbeplanned on enclose yards used for the parking of cars, scooters, etc.Where, however, theproblemscannotberesolvedbyplanning,theprovisionofdoublewindowsmaybenecessary.

9.4.8.3.2 Detailedplanning9.48.3.2.1Noisereductionwithinrooms

The reverberation time should not exceed 1.0 s in all general offices of the types listed in9.4.8.3.2.2 to9.4.8.3.2.6. In smallprivateoffices, the reverberation time shouldnot exceed0.75 second, in very large offices the reverberation timemay be increased to 1.25 s. Forcanteens,therecommendedmaximumreverberationtimeis1.25s.

9.4.8.3.2.2 Largegeneraloffices

Thegroupingofdepartmentsandmachinestogetherinoneroomshouldbeavoidedwhereverpossible. Where supervision is necessary, the provision of glazed screens carried up to theceilingshouldbeconsidered. If it isessentialtothework foranoffice formachineoperatorsandclerkstoworksidebysideinthesameroom,themachinesshouldbeenclosedbypanelsorlow screens lined with absorbent material and the ceiling should be sound absorbent. Inaddition, themachines shouldbe asquiet aspossible inoperation andmountedon suitableresilientmountings.NoteAquietareashouldbeplannedforprolongedtelephonicconversation.

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9.4.8.3.2.3 Lightweightconstruction

Modern constructionmethods and economy dictate the use of lightweight construction formanyofficebuildings.Whilethetightweightmaterialsleadtofastfabricationanderectionandalsoeffectconsiderableeconomyinthebuildingstructure,theymayleadtotremendoussoundinsulation problems between adjacent offices and areas. Light weight construction is alsofrequently employed for the subdivisionof large space into executive cabins and secretarialareas. Where suchconstruction isconsidereddesirable,efforts shouldbemade toprovideadoubleskinpanel. Thepanelsshouldbe isolated fromeachotheras faraspossibleeitherbytheuseof separate framingorby theuseofelasticdiscontinuities in theconstruction,andasoundabsorbingmaterialmaybeintroducedintheaircavitybetweenthepanel.Thepartitionsshould be full height up to thebottomof the roof above and anyopenings required for airmovementshouldbeprovidedwithsoundattenuatorscompatiblewiththerestofthepartition.Whenlightweightfloorsareprovidedinmultiusebuildings,adequateattentionshallbepaidtothequestionofairborneandstructurebornenoisetransmissionfromtheupperfloorstothefloors below. For effective reduction of airborne noise, a double panel hollow floorconstructionmaybeemployedwithsomeheavysounddampingmaterial introducedbetweenthepanelsandthepanelisolatedfromeachother.Thesounddampingmaterialcouldbesand,mineralwool,etc. Incase impactnoise isolation isalso required, theupperpanel shouldbeeffectivelyisolatedfromtherestofthefloorsandbuildingstructure.Thechoiceoftheisolationlayerwouldofcoursedependuponthelowestfrequencyofinterest.Anotherpointtobekept inmindwhengoing infor lightweightconstruction istoensurethatthe lightweightpanels arenot in resonancewith thenatural frequenciesof anymechanicalequipment installed inside thebuilding. Lightweightmaterialshavehighnatural frequencieswellwithintheaudiorangeandmayresonateorvibrateduetoanappliedvibratoryforce.Thisvibratory force is caused by mechanical equipment, road traffic, rail traffic, etc. Specialmeasuresalsoneedbe taken to isolateeither the sourceor thebuilding soas to reduce theamountofvibrationtransmittedtothebuildingstructure.

9.4.8.3.2.4 Openplanoffices

Anewconcept inofficeplanning is theuseofopenplanoffices. Largeopen floorspacesareconverted intoanofficeareawithseniorexecutives, juniorexecutivesandsecretarialstaffallseatedwithinthesameareawithouttheuseofanypartitionsorwalls. Whilethismethodofplanningisappreciated,itleadstoaproblemofinadequateacousticalprivacybetweenadjacentworkspaces.Speechprivacyinopenplanofficesisdefinedbythespeechinterferencelevelofintrudingnoise.Speechprivacybetweentwoadjacentroomsorspacesis,therefore,afunctionoftwokeyparameters;noisereductionoftheinterveningpartitionandbackgroundnoiselevels.Specialdesignmeasuresare,therefore,requiredtoreducethelevelofintrudingsoundsatworkplaces to acceptable low value so that people are not disturbed and adequate privacy ismaintained. Somespecialmeasureswhichmightbeconsideredforsuchopenplanofficesaretheuseofanacousticalceiling togetherwithpartialheightbarriersbetweenworkspaces,alldesignedtoprovideadequateprivacybetweenadjacentworkspaces.Inadditionusemayhave

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tobemadeofanelectronicbackgroundmaskingnoisesystemwhichprovidesaconstant levelofagenerallyacceptablebackgroundnoiseintheentireofficearea.Themaskingnoisesystemisaveryusefulconcept inopenplanofficedesignbecauseby raising thebackground levelateveryworkplace,intrudingnoisesaremadelessdisturbing.Abackgroundmusicsystemcannotserveasanoisemaskingsystembecausethemusicdoesnothaveaconstantspectrumorsoundlevel. Infactthebackgroundnoisemaskingsystemmustbe introducedgraduallywithouttheknowledgeofemployees.Theairconditioningsystemcanalsobeusedtogeneratebackgroundmaskingnoiseifthenoiselevelfromthefans,ductsandgrillsissuitablytailoredtogeneratethedesired frequency spectrum. However, it is not simple to predict the noise level of airconditioning componentsaccurately. On theotherhand, theelectronic systemenablesboththelevelandthespectrumofthebackgroundnoisetobeaccuratelyadjustedtosuitindividualjobrequirements.

9.4.8.3.2.5 Officeequipmentrooms

It is important thatmachines like typewriters,printer,etc.shouldbequiet in themselvesandalsobefittedwithresilientpads,topreventthefloorsortablesonwhichtheystandfromactingas large radiatingpanels. It isdesirable to locatemachines furtherapartand toapply soundabsorbenttreatmenttotheceiling.

9.4.8.3.2.6 Bankinghalls

Ifbankinghallsarelargeanlofty,noisenuisancetendstobeaggravated.Itisadvisabletoavoidhigh reflectiveceilings. Theworsteffectsmaybe reducedby segregating thenoise from thequietoperationsandscreeningonefromtheotherandbyapplyingsoundabsorbentmaterialstothesurfacesoftheceilings,screensandnearbywalls.Resilientflooringisalsorecommended.

9.4.8.3.2.7 Publicofficesandwaitingspaces

Noisenuisancemaybeminimizedbytheprovisionofresilientflooring,soundabsorbentceilingsandheavyfullheightscreensbetweenthepublicspaceandtheclericaloffice.

9.4.8.3.2.8 Canteens

Theprovisionofa soundabsorbent ceiling, resilient flooringand theuseofplastic traysandtableswithquiettopsarerecommended.

9.4.8.3.2.9 Circulationspaces

Theeffective lengthof longcorridorsshouldbe limitedbyproviding swingdoorsat intervals.Hardfloorfinishesandboardandbattenfloorsincorridorsshouldbeavoided.Theprovisionofasoundabsorbentceilingincorridorsisrecommended.Floorductsshouldbeplannedononesideofcorridors.Thenoisefromslammingofdoorsmaybereducedbyfittingautomaticquietactiontypedoorclosers. Door buffers are useful butmay reduce insulation of airborne sound due to the

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inevitable gaps between buffers. Continuous soft, resilient strip let into the door frames ispreferable.Theuseofquietactiondoorlatchesisrecommended.Staircasesandliftsshouldbeisolatedfromquietroomsandshouldhavesilenttypedoors.

9.4.8.3.3 Requirementofsoundinsulation

Withopenwindow(singleordouble)thesoundreduction(Dw)willbe510dB,andwithsealeddoublewindows itwillbe4045dB. Intermediatevaluesareobtainablewithclosedopenablewindows (singleordouble)butonly,ofcourse,atsuchtimesasventilationmaybedispensedwith. Having to choose between ventilation and noise exclusion is a serious handicap toefficientworkinginoffices.Inlargeofficeblocksonnoisysites,considerationshouldbegiventotheprovisionofsealeddoublewindowsandmechanicalventilationatleastintheofficesonthesidesofthebuildingexposedtonoise.

9.4.8.3.3.1 Theinsulationnecessarybetweenadjoiningrooms,bothhorizontallyandvertically,dependsupon the amountofnoise createdwithin the rooms, the amountof intrudingnoise andwhether it is important that conversation should not be overhead between rooms.Generallya sound isolation value (Dw)of30dBbetweenone roomandanother room inofficeisrecommended.

9.4.8.3.3.2 The following listmaybeconsideredasbroadclassificationofnoiseproducingroomsandrooms requiring quiet though many offices fall into both categories. Where rooms inopposingcategoriesareplannedadjacenttoeachother,asoundreduction(Dw)ofat least45dBshouldbeprovidedbetweenthem.

NoiseProducingRooms

RoomsRequiringQuietConditions

Entrancehalls,staircasesandcorridorsusedbythepublic

Executives rooms, ConferenceroomsandBoardrooms

Liftsandlifthalls InterviewroomsMotorandplantrooms OfficesforoneortwopersonsLavatories MedicalofficersroomsPublicoffices SickroomsCanteenandkitchens RestroomsOfficemachinerooms LibrariesRecreationrooms TelephoningroomsLargegeneraloffices Cinemasandprojectionrooms

a) roomsrequiringquiet(aslisted45dBabove)onaquietsitewhereprivacyisrequired;

b) roomsrequiringquiet(aslisted40dBabove)butonanoisysiteorwherealowerdegreeofprivacyistolerable;

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c) clericalofficesinwhichnoiselevelsof2030dBnotconstituteamajornuisance.9.4.8.3.3.3 Itisrecommendedthattheminimumsoundreductionindex,Rwforfloorsshouldbe45dB,

andthefloorsshouldhavearesilientfinish.9.4.9 HOTELSANDHOSTELS9.4.9.1 General

Hotels and hostels are primarily used as dwelling units, and hotels also provide for publicentertainment. Themost serious risk of course is disturbance to sleep, and adequate care,therefore,needbetakentoprotecttheoccupantsfrombeingdisturbedbyoutdoorandindoornoise.

9.4.9.1.1Outdoornoise

Hotelsnearrailwaystations,airports,highwaysandthosesituatedinhighlyurbanizedareasareespeciallyvulnerabletooutdoornoise.Theoutdoornoiseinmanyoftheareasisofahighleveleven late at night and in the earlymorning. Thenoise could alsobedue toother typesofactivities suchasbuilding constructionactivity (piledriving, concretemixing,etc)andvarioustypesofportableutilityequipment,suchascompressorsorgenerators.

9.4.9.1.2 Indoornoise

In so far as indoornoise is concerned, thenoise couldbedue to theoccupants themselves,which istransmittedfromoneroomtotheother. Itcouldalsobeduetopublicfunctionsandlatenightuseofrestaurantslocatedinthehotelasalsoduetomiscellaneousutilityequipmentinstalled for providing and maintaining the services in the hotel, such as, air conditioningequipment,pumpingequipment,powerlaundryandkitchen.Sometimeshotelsequippedwithstandby generators are a potential source of noise. Another source which could lead todisturbancetotheoccupantsistheplumbing.

9.4.9.2 Recommendations9.4.9.2.1 Siteplanning

While it is desirable to locate the hotel, or hostel away from an areawhere there is a highambientnoiselevel,manyatimethesehavetobelocatedinnoisyareasforpublicconvenience.Hotelsnearairportsandrailwaystationsarebecomingpopularbecausetheyareconvenientforpassengers intransit. Hotels located inthecommercialareasofacityarealsoacommerciallyviablepropositionandmanya time this factoroutweighs theotherproblemsassociatedwithsuchalocation.Whenareasonablyquietlocation isnotpossible,itisdesirablethatadequatemeasuresbeconsideredtoprovideacomfortableacousticalenvironmentfortheoccupants.

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9.4.9.2.2 Internalplanning

Where ahotel is located in anoisy environment, theprovisionof sealedwindows (singleordouble)andprovisionofanairconditioningsystemisdesirableforroomsexposedtonoise.Therequirementsforthewindowswouldofcoursedependuponthelevelandcharacterofnoiseinthearea.Thegeneralrecommendationsforsatisfactoryacousticaldesignofhotelsaregivenin9.4.9.2.2.1to9.4.9.2.2.7.

9.4.9.2.2.1 Hotelsofallclassesshallbynecessityprovidegoodprotectionagainst indoornoise. Since

hotels canbe consideredas flats, the standardsofprotection recommended for flatsarealsoapplicabletohotels.Partitionbetweenguestroomsandbetweenrooms,corridorsandfloorsshallnotbelessthan115mmbrickwallplasteredorequivalent.Thefloorsshallhaveproper impact insulation. Special attention should be paid to builtinwall cupboards asthese are potential areas of sound leakage. These will not serve as sound insulatingpartitionsandmaynotberelieduponto increasethe insulationvalueofpartitionsagainstwhichtheymaybebuilt.Infact,partitionsbetweenadjoiningroomsshouldbecontinuousbehind the cupboards. Useof silent typedoor gear and cupboard catches is alsohighlydesirable.

9.4.9.2.2.2 Dooropeningsonoppositesidesofcorridorsshallbestaggeredanddoorsbeprovidedwith

gasketsonhead,sidesandthreshold. Intercommunicatingdoorsshouldbedoubledoors,fully gasketed. Doors should also have quiet action latches. Whenever possible, roomsshould be entered through a baffle lobby. Wherever possible, corridorwalls should nothaveventilatorsunlesstheyaredoubleglazedandnonopenable.

9.4.9.2.2.3 Corridorsandstaircasesmayhaveresilientfloorcoveringsandsoundabsorbentceilingsare

desirableunlessthecorridorisfullycarpeted.Staircasesandliftwellsmaybecutofffromcorridorsbymeansofswingdoorsand,ifpossible,isolatedfromguestroomsbylinenstoresorsimilarrooms.Roomservicepantriesonfloorscanalsobeasourceofnoiseandmaybeseparatedfromcorridorsbybafflelobbies,unlesstheroomsthemselveshavebafflelobbies.

9.4.9.2.2.4 Exceptwithinthesamesuite,bathroomsshouldnotbeplannednexttobedrooms.Where

thisisunavoidable,internalpipeshaftswithheavywalls,unpiercedonbedroomssidemaybeusedasmeansofseparation.Itisimportanttochoosequiettypeofsanitaryfittingsandtodesign theplumbingsystemsoasnot tocreatenoise, that isbyavoidingsharpbends,restrictionsofflow,quickactionvalvesthatmightcausewaterhammer,etc.

9.4.9.2.2.5 Airconditioningsystemshouldbequietinoperation.Careshouldalsobetakenthattheair

conditioningductsdonotleadtoacrosstalkproblembetweenrooms.Suitableacousticalliningwouldneedtobeprovidedintheductsconsistentwiththefiresafetyrequirementsofthebuildings.

9.4.9.2.2.6 Largehotelsoftenhavebanquethallsandconferencehallswhichareseparatelyhiredout

forpublicandprivatefunctions.Latenightrestaurantsandnightclubsarealsopopularand

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functionsinalltheseareasmaygoonwellintothenight.Itisthereforeessentialthattheseroomsbeeffectivelyisolatedfrombedroomsandeffectiveinsulationformallpossiblenoisesource is considered. Here it is not only necessary to consider the airborne soundinsulationbut it isalsonecessary to consider thequestionof structureborneand impactnoisetransmittedfromareaswheretheremightbedancinglateintothenight.

9.4.9.2.2.7 Whilemostofthenoiseproblemsencounteredinhotelsareapplicabletohostels,the

latterarenormallyofmoreeconomicalconstructionand,therefore,cannotcaterforspecialsound insulationprovisions. However,as faraspossible,precautions shouldbe taken toprovidecomfortableconditions inhostelrooms. This isespeciallytrueforstudenthostelswhereeachroom isalsoa livingroom.Studentsmightplaymusicorhave louddiscussionslateintothenight.

Thismaydisturbsleeporstudyofotherstudents.Properprecautionsshould,therefore,betakentoprovidesatisfactoryconditions.

9.4.10 INDUSTRIALBUILDINGS

9.4.10.1General

Industrialbuildingsareprimarilyproducersratherthanreceiversofnoise.Thelevelofindustrialnoise commonly exceeds that from any other source with the exception of aircraft. Ascomparedwith traffic noise, its effects are lesswidespread but it is oftenmore annoying incharacter.

9.4.10.1.1 Many industrialnoisescontainverystronghigh frequencywhines,screechesandclatter

these components are relatively more attenuated by passage through the air and by theinsulationoflightstructurethanarelowerfrequencies.

9.4.10.2Sourcesofindustrialnoise9.4.10.2.1 Noises in industrial buildings are mainly of indoor origin. Noise in factories and

workshops is generally caused bymachine tools and by operations involved inmaking andhandlingtheproductandtheyareclassifiedintothefollowinggroups,dependinguponhowthenoiseenergyisgenerated.

9.4.10.2.1.1Impact

Noisecausedbyimpactisthemostintenseandwidespreadofallindustrialnoises.Itisnormallycoupledwithresonantresponseofthestructuralmembersconnectedtotheimpactingsurface.Commonsourcesofthistypeofnoiseareforging,riveting,chipping,pressing,tumbling,cutting,weaving,etc.Intenseimpactnoisemayalsobeproducedduringhandlingofmaterialsasinthecaseofshearedsteelplatesfallingoneoveranotherincollectingtraysinasteelfactory.Impactnoiseisusuallyintermittentandimpulsiveincharacter,butitmayalsobecontinuousasinthecaseoftumbling.

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9.4.10.2.1.2Friction Mostofthenoiseduetofrictionisproducedinsuchprocessesassawing,grindingandsanding.

Frictionalsooccursat the cuttingedgeon lathesandothermachine toolsand inbrakesandfrombearings. The spectrumof frictionalnoiseoftenpredominates inhigh frequencyand isveryunpleasantincharacter.

9.4.10.2.1.3Rotationandreciprocation

Arotatingorreciprocatingmachinegeneratesnoiseduetounbalancedforcesand/orpressurefluctuationsinthefluidsinsidethemachines.Inmanycases,themovingsurfacesradiatenoisedirectlyandinothercases,thepressurefluctuationsaretransmittedtotheoutercasingofthemachine fromwhere theyare radiatedasnoise. Interactionof rotating componentwith thefluidstreamcanalsogiverisetopuretonecomponents,suchasthewhine inaturbine. Sincemostmachine casings have radiation efficiencies of unity in the higher frequency range, theamountofsoundradiatedisoftensubstantial.

9.4.10.2.1.4Airturbulence

Noisemay be generated by rapid variation in air pressure caused by turbulence from highvelocityair,steamorgases.Commonexamplesaretheexhaustnoisefrompneumatictoolsandairjets.Thenoiseisintense,andbroadbasedincharacterandthefrequencycriteriadependsonthesizeofthejet.Theintensityincreasesrapidlywiththevelocityoftheairstream.

9.4.10.2.1.5Noiseswithpuretonecomponents Whiningnoisefromturbinesandhummingnoisefromtransformerscomeunderthisgroup.9.4.10.3Noisecriteria9.4.10.3.1Hearingdamageriskcriteria

Continuousexposuretohighnoiselevelsmayresultinpermanentnoiseinducedhearinglossinthe course of time. Damagerisk criteria specify themaximum levels and duration of noiseexposurethatmaybeconsideredsafe.Generallyaccepteddamageriskcriteriaforexposuretocontinuous,steadybroadbandnoiseareshown inTable7. Wheneverthesound levelsattheworkerspositioninafactoryexceedthelevelsandthedurationsuggested,feasibleengineeringcontrolsshallbeutilizedtoreducethesoundtothelimitsshown.Ifsuchcontrolsfailtoreducesound levels within the levels of Table 7, personal hearing protection equipment shall beprovidedandusedtoreducesoundlevelswithinthelevelshown.

9.4.10.3.2InterferencewithCommunication

Infactorieswhereaudiblewarningsignalsareused,orwhereanoperatorfollowstheoperationofhismachinebyear, thebackgroundnoise shouldnotbe so loud as tomask the signalordesired sound (the information sound) tobeheard. Noisemaybe thecauseofaccidentsbyhinderingcommunicationorbymaskingwarningsignals.

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9.4.10.4Methodsofreducingnoise9.4.10.4.1Noisecontrolbylocation

Machines,processesandworkareaswhichareapproximatelyequallynoisyshouldbe locatedtogetheras faraspossible.Areas thatareparticularlynoisy shouldbe segregated fromquietareasbybufferzonesthatproduceandmaytolerateintermediatenoiselevels.

9.4.10.4.2Noisereductionbylayout

The office space in an industrial facility should be as far as possible located preferably in aseparate building. This building should not have awall commonwith the production area.Wherea commonwall isunavoidable, it shouldbeheavywith few connectingdoorsandnopermanentopenings.

9.4.10.4.3Noisereductionatsource 9.4.10.4.3.1Selectionofmachinery

Noiseshouldbereducedasnearthesourceaspossible. Whiletheoperationalprocesses inafactorymaybefixedandmayhavenoquieteralternative,carefulselectionofthemachinetoolsandequipment tobeusedmayconsiderablyhelpattaining lowernoise levels in themachineshop.

9.4.10.4.3.2Reducingnoisefrompotentialsources

Impact that is not essential to a process should be quietened. Noise from handling anddropping of materials on hard surfacemay be reduced by using soft resilientmaterials oncontainers,fixingrubbertyresontrucks,trolleys,etc.Machinenoisemaybekepttoaminimumbypropermaintenance.Properlubricationwillreducenoisebyfrictionconveyors,rollers,etc.

Table7PermissibleExposureLimitsforSteadyStateNoise(Clause9.4.10.3.1)

SoundLeveldBA(ShowResponse)

TimePermitted,Thmin

85 160086 135687 120888 103489 91190 80091 65892 60493 51794 43695 40096 329

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97 30298 25099 215100 200101 144102 131103 119104 109105 100106 052107 046108 040109 034110 030111 026112 023113 020114 017115 015

Notes1 Wherethetabledoesnotreflecttheactualexposuretimesandlevels, thepermissibleexposuretocontinuousnoiseatasinglelevelshallnot ExceedthetimeT(inhours)computedfromtheformula:

)]85(2.0(216

= LT where ListheworkplacesoundlevelmeasuredindB(A). 2 Whenthedailynoiseexposureiscomposedoftwoormoreperiodsofdifferent Levels,theircombinedeffectshouldbeconsideredratherthantheindividual effectofeach.Thecombinedlevelsmaynotexceedadailynoisedose,Dofunity WhereDiscomputedfromtheformula:

n

n

TC

TC

TCD ++= .......

2

2

1

1

Where,C1,C2Cn indicate the totaldurationofexposure (inhours)atagiven steadystatenoise level;andT1,T2,..Tnare thenoise exposure limits (inhours) for the respective levelsgiveninthetableorcomputedbytheequationinNote1.Exposuretocontinuousnoiseshallnotexceed115dB(A)regardlessofanyvaluecomputedbytheformulaforthedailynoisedose,DorbytheequationgiveninNote2.

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9.4.10.4.3.3Thenoisefromtheradiatingsurfacingmaybereducedbyreducingtheradiatingarea.Forexample,iftheareaishalved,thenoiseintensitywillbereducedby3dBandatlowfrequenciesthereductionwillbemuchgreater.

9.4.10.4.3.4Supportingstructuresforvibratingmachinesandotherequipmentshouldbeframesrather

than cabinetsor sheetedenclosures. If an enclosure isused,precaution shouldbe taken toisolate it and line it on the inside with soundabsorbent material. The noise radiated bymachineryguardscanbeminimizedbymakingthemofperforatedsheetorofwiremesh.

9.4.10.4.3.5Reducingtransmissionofmechanicalvibration

A vibrating source does not usually contain a large radiating surface but the vibration isconductedalongmechanically rigidpaths tosurfaces thatcanactaseffective radiator. If therigidconnectingpathsare interruptedbyresilientmaterials,thetransmissionofvibrationandconsequentlythenoiseradiatedmaybegreatlyreduced.Thereductiondependsontheratioofthedriving(forcing)frequencyofthesourcetothenaturalfrequencymaybedeterminedformstatic deflection under actual load as given in Fig. 1. Higher the ratio between the twofrequencies, lesser isthetransmissibility,which isdefinedastheratiooftheforcetransmittedthrough the resilient isolator to the exciting force applied to it. Transmissibility and theequivalent noise reduction for various frequency ratios are given in Fig.2. For satisfactoryoperation,aratioof3:1ormorebetweenthedrivingandnaturalfrequenciesisrecommended.

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Materialsforisolatorsandtheirpositionaregivenbelow:

a) MaterialforIsolatorsVibrationisolatorsareusuallymadeofresilientmaterialslikesteelintheformofsprings,rubbercorkandfelt.

1) Because of the large range of deflections obtainable in coil springs, they may isolate

vibrationsoveralargespectrumoflowfrequencies.Metalspringstransmithighfrequency(from about two hundred to several thousand c/s) very readily. Transmission of thesefrequencies can be reduced by eliminating direct contact between the spring and thesupportingstructure. Rubberorfeltpadsmaybe insertedbetweentheendsofthespringandthesurfacestowhichitisfastened.

2) Rubberintheformofpadsmaybeusedtoisolateveryeffectivelyengines,motors,etc.Itmaybeusedincompressionorinshear.Somerubbermountingsuserubberinshearastheprimary elastic elements and rubberincompression as a secondary element whichfurnishessnubbingactionifthemountingissubjectedtoanoverload.

3) Feltorcorkorbothmaybeusedasresilientmatsorpadsundermachinebases. The load

perunitareashallbechosentoproduceenoughdeflectionforthe isolationrequired;andshallbesuchthatatthisdeflection,itisnotloadedbeyonditselasticlimit.

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b) Positionof IsolatorThenormalpositionof the isolators isbetween themachineand its

foundation. However, iftheforcingfrequencyofthemachine is low(lessthan10H2)andvibration isolators with the requisite deflection for this location are not available, themachinemay be bolted directly to an independent heavy inertia concrete base and theavailablevibrationisolatorsusedbelowtheconcretebase.1) Largepressanddrophammerswhichcreateseriousimpactvibrationinheavymachine

shops may be mounted rigidly on very massive blocks of concrete having weightsseveral timesgreater than theweightsof thesupportedmachines. The inertiablocksmay, inturn,be isolated fromthebuildingstructureby largewoodenblocksandwiththickpadsofcork.

2) In critical installations (see Note), attempt should be made to locate the resilient

mounts inaplanewhichcontainsthecentreofgravityofthemountedassembly. It isalsopreferabletolocatethemountslaterallyasfarawayaspossiblefromthecentreofthemachine.

NoteCritical installationsare those installationswhere transmissionofvibration from

theseinstallationswillseriouslyhamperthenormalworking.

3) Rigidmechanical ties between vibratingmachine and building structure, shortcircuit orreducetheeffectivenessof isolators. Looseandflexibleconnectionsshouldbe inserted inallpipesandconduits leavingfromthevibratingmachine. Whereflexibleconnectionsareimpracticable,bendsshouldbe inserted into thepipesor thepipes themselvesshouldbesupportedonvibrationmountsforaconsiderabledistancefromthesource.

4) Flexibility of foundation The effect of flexibility of the foundation on the isolator

transmissibility shall be considered in the selection of practical vibration isolatingmountings.Thesimplifiedvibrationisolationtheoryassumesacompletelyrigidfoundation.However, in practice, this can never be achieved. The foundation is never actuallycompletelyrigid. Generally,therelatively lowstiffnessofthe isolationsystempermitstheassumptionofthefoundationtoberigid.However,ifthestiffnessoftheisolatorisallowedtobecomecomparabletothefoundationstiffness(orgreater),thedeflectionoftheisolatorwillbecomesmallerandthefoundationwillalsodeflectwithincreasedtransmissibilityanddecreased isolatorefficiency. Inadynamic sense, supporting foundationor floors shouldhavenatural frequencyashighandbeas stiffaspossible compared to the systembeingisolated.Gooddesignpractice requires that the isolators shouldbedesigned assuming arigidfoundationwiththestipulationthattheselectedmachine isolationsystemfrequencyshouldbewellbelowthefoundationfrequency.Thispointshouldspeciallybekeptinmindwhen installingmachines at upper levels in buildings because supported slabs generallyhave lowernatural frequencies (lowstiffness) than slabsongrade inbasementorgroundfloorlocations.

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9.4.10.4.4 Noisereductionbyenclosuresandbarriers

9.4.10.4.4.1Enclosures

Airbornenoisegeneratedbyamachinemaybereducedbyplacingthemachineinanenclosureorbehindabarrier.Theenclosuremaybeintheformofclosefittingacousticboxaroundthemachine such that the operator performs his normalwork outside the box and thus is notsubjectedtothehighnoise levelsofthemachine. Theenclosuremaybemadeofsheetmetallinedinsidewithanacousticalmaterial.

Where size of the machine, working area and the operation do not permit closefittingenclosures, themachinemay be housed in a room of its own. The inside of the enclosureshould be lined with soundabsorbingmaterials to reduce the noise level of the containedsound. The boundingwalls of the enclosures shall also have adequate transmission loss toprovidedesiredinsertionloss.

9.4.10.4.4.2 BarriersA partial reduction of noise in certain directions may be obtained by barriers or partialenclosuresorpartialheightwalls.Twosidedorthreesidedbarrier,withorwithoutatopandinvariably covered on themachine sidewith acoustic absorptionmaterial should face awallcoveredwithsoundabsorbingmaterial.Ifthetopoftheenclosuresisopen,thereductionmaybeincreasedbyplacingsoundabsorbingmaterialontheceilingoverhead.

9.4.10.4.5 Acousticabsorptiondevices

9.4.10.4.5.1 Acoustictreatmentofceilingsandsidewalls

Inordertoreducethegeneralreverberantnoiselevelinmachineshops,acousticalmaterialbeplacedontheceilingandsidewalls.Withthistreatment3to6dBreductionofmiddleandhighfrequencynoisemaybeachieved. Whilethenoise levelatthesource,affectingtheoperator,maynotbereducedmaterially,thetreatmentwouldbringdownthegeneralnoise levelawayfromthesourceinreverberantfield.

9.4.10.4.5.2 Functionalaroundabsorbers

For efficient noise reduction functional sound absorbers may be clustered as near themachinesaspossible. Theseunitsmaybesuspendedanddistributed inanypatterntoobtainlower noise levelswithin themachine shop. Compared on the basis of equal total exposedsurfaceareas, functionalsoundabsorbershavehighernoise reductioncoefficients (NRC) thanconventionalacousticalmaterialsplaceddirectlyonceilingsandwalls.

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9.4.11 LABORATORIESANDTESTHOUSES

9.4.11.1Sourcesofnoise

9.4.11.1.1Outdoornoise

Inatesthouseorlaboratory,whereresearchworkersandscientistsareengagedinperformingsophisticatedexperiments,theexternalnoise ismostlycontributedbynoiseemittingbuildings(workshops,machinerooms),airports,railwaystationsandgeneraltrafficnoises.Theoutdoorsourcesofnoiseinacollegelaboratoryincludenoisesproducedinaplaygroundaswell.

9.4.11.1.2Indoornoise

The following sources mainly contribute to indoor noises in research institutions/collegelaboratories.

a) workshops,machinerooms,cafeteria,etc.;b) airconditioningandexhaustfans;c) noiseproducedwithinthetesthouseorlaboratorywhileperformingexperiments;andd) typingorothermachinenoises,telephoneservice,lift,sanitaryservices,etc.

9.4.11.2 Recommendations

9.4.11.2.1 Siteplanning

Whileplanningfora laboratoryortesthouse,careshouldbetaken inthedesignthatnnoiseemitting installationsshouldexist in itsneighbourhood. However,whereoutdoornoisesexist,suchasfrom localfactory,heavytrafficairports,railway lines,sportgroundsorbusymarkets,buildingsshouldbekeptasfarawayaspossiblefromthesourceofnoise.

9.4.11.2.1.1Thewindowanddooropenings towards thenoisesourcesshouldbeminimal. Minimumamountofglazingshouldbeplacedonwallsdirectlyfacingthenoisesources.

9.4.11.2.2Internalplanning

9.4.11.2.2.1Noisyplacesshouldbekeptseparatefromthequietones.Thelocationoflaboratoriesortesthousesshouldbesochosenthatitiscutofffromthenoisyzones.Wherethereareofficesattached toa laboratory,provision shouldbemade to treat theofficesand touseacousticalpartitions,toachieveasoundisolationDwatleast35dB.

9.4.11.2.2.2 In a laboratory, mostly hard reflecting surfaces and bare furnishings are found, whichproduce very reverberant conditions. The noise condition still deteriorateswhen noiseproducing instrumentsareswitchedonoraheavyobject isdroppedon the floor. Undertheseconditions,soundabsorbingtreatmentofthespaceisveryessential.Soundabsorbingceilingsarerecommendedtodeadensuchnoises.Rubberbuffersmayalsobefittedtothelegsoffurniture.

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9.4.11.2.2.3 In largespan laboratoriesor testhouseswherescientistsand researchersareengaged inwork and/or simultaneously busy in calculations or desk work requiring high degree ofmentalconcentration,useofsoundabsorbingscreensisrecommended.

9.4.11.2.2.4 Noisereductionbetween the testhouseor laboratoryandcorridorsorgeneralcirculation

spaceshouldbewellkeptinmindandduecareshouldbetakenofthetypeofdoorsandthemannerof their fittingsetc. Transmissionofnoise through serviceducts,pipes, liftsandstaircasesshouldalsobeguarded.

Telephones should preferably be placed in a separate small enclosure or acousticallyefficienttelephonebooth.

9.4.11.2.2.5 To isolatea laboratoryoratesthousefromstructurebornenoisesoriginatingfromupperfloor,sandwichtypefloorconstructionisrecommended.

9.4.11.2.2.6 Wherever theprovisionofdoubleglazedwindows isnecessary to reduce theheat losses,

care should be taken to provide sealed doublewindows rather than double glazing in asinglewindow.

NoteDoubleglazedwindows for sound isolation shouldhaveaminimumgapof100mmbetweenthetwoglasses.

9.4.12 MISCELLANEOUSBUILDINGS

9.4.12.1Lawcourtsandcounselchambers

Itisimportantthatlawcourtsandcouncilchambersbeprotectedfromtheintrusionofoutdoornoise and from indoor noise arising both from ancillary offices and circulation spaces. Thegeneral recommendationson siteplanning given inPart3apply to law courtsandmunicipalbuildings,but in the largerbuildingsat least, furtherprotectionagainstoutdoornoisecanbeobtained by planning offices and other rooms around the court rooms or chambers, andseparating the offices from the central rooms bymeans of corridors. This arrangement isusuallyconvenienttothefunctionofthebuildings.

9.4.12.1.1 Thewallbetween thecorridorsand thecentral roomsshouldhaveasound reductionindex,Rw,ofnotlessthan50dB(forexample230mmbrick)toinsulateagainstairbornenoiseinthecorridors.Entrancesfromhallsorcorridorsintocourtroomsorcounselchambersshouldbe throughbaffle lobbieswith twosetsofquietactiondoors. Soundabsorbing treatmentonceilingsandupperpartsorwallsorentrancelobbiesisrecommended.

9.4.12.1.2 Thewholeofthefloorofthecourtroomorchamber includingstepsandseatingareassetasideforthepublicshouldhavearesilientfloorfinishtoreducethenoiseoffootstepsandshufflingoffeet.Anytipupseatsshouldbequietinaction.

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9.4.12.1.3 Soundabsorbingtreatmentappliedforacousticpurposesservesalsotoreducethebuildupofnoisewithin the room and,partof the treatment shouldbe applied in aband to theperimeteroftheceilingtoabsorbintrudingoutdoornoise.Itisoftendesirabletokeepthecentrepartoftheceilingfreeofabsorbentmaterialforacousticreasons.

9.4.12.2 Libraries,m