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CHAPTER1
INTRODUCTION
1.1ACOUSTICNOISEANDNECESSITYOFITSREDUCTION
Acousticnoiseisoneofthemostseveresideeffectsaccompanyingrapid
developmentofindustryandtransport,andequippingresidentialroomswith
differentsortsofdevices.Generally,noisecanbeofanarrowbandorbroadband
character[KuoandMorgan,1996],[Pawelczyk,2005].Narrowbandnoise
concentratesmostofitsenergyatspecificfrequencies.Itisgeneratedbyrotatingor
reciprocatingmachines,soitispurelyperiodic(deterministic)ornearlyperiodic
andisdominatedbyoneormanytones.Broadbandnoiseiscaused,forexample,
byturbulenceandthereforedistributesitsenergyacrossawidefrequencyrange.In
someenvironmentsimpulsivenoisecanalsobedistinguishedasasingleorseries
ofacousticeventswithshortduration,usuallylessthan1s[Vaseghi,2000].
Prolongedexposuretohighlevelnoisemaydamagethehearingsystemand
deteriorateotherbasichumansystems.Therefore,accordingtothelaborlawthe
worktimeduringthedayshouldbelimitedorappropriateprotectionmeansused.
Ontheotherhand,thenoiseimpairsconcentration,maybeacauseofaccidents,
andmakescommunicationdifficult,therebysufficientlyreducingworking
efficiency.Inhouseholdsitannoysanddoesnotallowtorestfully.
