托福听力十大必背段子4.doc

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1、托福听力十大必背段子44.991040生活段子：噪音影响　　I'mgradtoseesomanyofyouhere.We'vebecomereallyalarmedoverthehealthcenterbythenumberofstudentsweareseeing,whoareexperiencinghearingloss.First,Iwanttogooversomebasicabouthearing.Thenwecantakealookatourschoolenvironmentandseeifwecanfigureoutsom

2、ewaystoprotecthearing.Theleadingcauseofpreventablehearinglossisexcessivenoise.Toomuchmoderatenoiseforalongtimeorsometypesofintensenoiseforevenashorttimecandamagehearing.Loudnessismeasuredinunitscalleddecibels.Onedecibelisthelowestsoundthattheaveragepersoncanhere.Soundsu

3、pto80decibelsgenerallyaren'tharmful.That'snoiseliketrafficonabusystreet.Butanythinglouderthan80decibels,especiallywithcontinuousexposure,mayeventuallyhurtyourhearing.Onceyouareuptoaround140decibels,that'slikeajetplanetakingoff,thenyoumightevenfeelpaininyourears.Andpains

4、aresuresignthatyourhearing'satrisk.Evenoneexposuretoareallyloudnoiseatcloserangecancausehearingloss.Sowhatyouneedtodoislimityourexposuretoharmfullevels.Ifyoupassalongthishandout,wecantakealookatthedecibellevelofsomecommoncampussounds.Noticehowloudthosehornsarethatpeople

5、taketofootballgames.Theyarereallydangerousifblownrightbehindyou.Now,let'strytogeneratealistofdamagingnoises