10噪音人类的杀手

10、Noise,KillerofMankindUnwantedsound,ornoise,suchasthatproducedbyairplanes,traffic,orindustrialmachinery,isconsideredaformofpollution.Noisepollutionisatitsworstindenselypopulatedareas.Itcancausehearingloss,stress,highbloodpressure,sleeploss,distraction,andlostproductivity.Soundsareproducedbyobjectsthatvibrate1ataratethattheearcandetect2.Thisrateiscalledfrequencyandismeasuredinhertz3,orvibrationspersecond.Mosthumanscanhearsoundsbetween20and20,000hertz,whiledogscanhearhigh-pitched4soundsupto50,000hertz.Whilehigh-frequencysoundstendtobemorehazardous5andmoreannoyingtohearingthanlow-frequencysounds,mostnoisepollutiondamageisrelatedtotheintensityofthesound.Measuredindecibels6,noiseintensitycanrangefromzero,thequietestsoundthehumanearcandetect,toover160decibels.Conversationtakesplaceataround40decibels,asubwaytrainisabout80decibels,anda