《英語中高職貫通第》課件-lesson 7

Workinsmallgroupsandnameatleastfiveusesofsoundinourlife.1.2.3.4.5.6.Communication:peopletalktoeachother.Entertainment:peoplelistentomusic.Alarming:securityalarm;alarmclockLiftingandmovingobjects:Doctorsusetheultrasonicdevicetoremovetinystonesfromthehumanbody.Conveyinginformation:theradiobroadcastsnews.Howdoessoundtravelinair?InPictureA,themanistalking;whileinPictureB,themanislistening.Drawtheshapeofthewaythatsoundtravelsinbothpictures.Measuringdepthsofoceans:Scientistsuseultrasoundtomeasurethedepthsofoceans.Inthefollowingreadingpassage,locatethecorrectinformationforthefourpicturesbelowandthenwritebriefsummariesonthelines.BriefSummary:BriefSummary:Astronautshavetouseradiostocommunicateinspacebecausesoundcannottravelthroughavacuum.Soundisconveyedthroughthestringofatin-cantelephone.BriefSummary:Soundwillnottravelthroughavacuum.BriefSummary:Liquidsandsolidstransmitsound.SoundWavesWehearthingsduetothetransferenceofsoundfromitssourcetoourears.Soundisawavemotionthatisofgreatimportancetohumansandtootheranimals.Mostofourcommunicationisachievedthroughtheuseofsound.Manyanimalsalsocommunicateusingsound—forexample,itisbelievedthatwhalescancommunicateoververylargedistancesduetosoundtransmittedthroughthewater(amuchbettertransmitterofsoundwavesthanair).Soundisalsousedforpurposesotherthandirectcommunication.Ultrasounddevicesareusedtomeasureoceandepthsandsurveyoceancontours,andareaveryusefulaidtodiagnosisinmanymedicalinvestigations.Inthisarticle,wewilllookatsomemediumsthroughwhichsoundtravels.Considertheexperimentshowninoneofthepicturesabove.Anelectricbellissuspendedbyarubbercordinabelljarsealedtoaflatmetalplace.Theleadstotheelectricbellpassthroughanair-tightrubberstopper.Thebellisconnectedtoabatterysupplyandsetringing.Itcanbeheard.Thebelljarisconnectedtoavacuumpumpandsomeoftheairisremovedfromthebelljar.Astheairisremovedfromthebelljarthesoundoftheelectricbellbecomesfainteruntil,ifasufficientlylowairpressureisreached,nosoundcanbeheardatalleventhoughyoucanstillseethehammeroftheelectricbellvibrating.Iftheairisallowedtoreturnslowlytothebelljar,thesoundwillbeheardagain.Itisessentialthatthebellissuspendedinthespaceinthebelljaranddoesnottouchthemetalplate,otherwisesoundcouldbetransmittedthroughthemetalplatetotheairoutside.Thesoundreachesthelistener'searbytransmissionthroughtheair(andtheglassofthebelljar).RobertBoylefirstperformedthisexperimentaround1660.Itillustratesthatsoundcannottravelthroughavacuum.Whilesoundandlightarebothformsofenergy,inthisway(andothers)soundisdifferentfromlight,becauselightdoestravelthroughavacuum.Outerspaceisavacuum,soastronauts“walkinginspace”cannottalktoeachotherbynormalmeans.Sounddoesnottravelthroughspace,sotheymustcommunicatewitheachotherbyradio.Radiowaves,beingelectromagneticwaves,cantravelthroughavacuum.Ifthebelljarintheexperimentisfilledwithothergases,e.g.carbondioxide,itcanbeshownthatthesegaseswilltransmitsound.Wheneverthereisanygasinthebelljar,thesoundofthevibratingelectricbellcanbeheard.Soundtravelsthroughgases,butwhataboutliquidsandsolids?Ifyouputyourheadunderwaterinaswimmingpool,youcaneasilyhearthesoundmadeiftwostonesarerubbedtogetherunderthewaterbysomeoneelseafairdistanceaway.Thesoundwavesarecarriedtoyourearbythewater.Also,therubbingofthetwostonesunderwaterwillbelouderthanyouwouldexpect,assoundtravelsthroughliquidsbetterthanitdoesthroughair.Anotherwayofdemonstratingthesameeffectistouseatuningfork.(Tocausethetuningforktovibrate,strikeitonarubberstopperabouthalfwayalongoneprong.)Ifavibratingtuningforkisheldintheairitisbarelyaudible.Ifawoodendiscisfittedtotheshaftofthetuningforkandthenthevibratingtuningforkisplacedwiththewoodendisconthesurfaceofwater,thesoundwillbehearddistinctly.Thetuningforkwillalsobedistinctlyheardifitsshafttouchesatable.Coveroneearandplacetheotherearononeendofawoodenbench.Asksomeonetotaptheotherendofthebench.Youwillbeabletohearthesoundasittravelsthroughthewood.InWesternmoviesAmericanIndiansandcowboysaresometimesshownputtingtheirearstothegroundtolistenfortheapproachofhorses.Thetableandthegroundintheseexamplesbothenablethesoundtobetransmittedfromitssourcetoyourear.Wehavenowseenthatsolids,liquidsandgasesareallconductorsofsound.Soundneedsamaterialmediumforitstransmission.Atin-can“telephone”demonstratesthatsoundtravelsthroughsolids.Whenthestringbetweenthecansispulledtight,soundcantravelalongit.Onepersoncanspeakintooneofthetin-cansandtheotherpersoncanhearthroughtheothertin-cansomedistanceaway.Someexperimentsarelistedinthepassage.Whatconclusion(s)doeseachofthemreach?Workinagroupandfinishthefollowingchart.Soundcannottravelthroughavacuum.Soundcantravelthroughliquidsandsoundtravelsthroughliquidsbetterthanitdoesthroughair.Soundcantravelthroughliquidsandsoundtravelsthroughliquidsbetterthanitdoesthroughair.Soundtravelsthroughthewood/solids.Soundtravelsthroughsolids.Whichisagoodconductorofthesound?Explainyourreasonsbasedonthearticleyouhaveread.Writepropertermsforthepartsinthepicture.batteryrubberstopperrubbercordvacuumvacuumpumpTheNoiseControlClubAstudenthasorganizedtheNoiseControlClub.Andheisnowspeakingtoagroupofstudentsoncampusinordertorecruitnewmembers.Listentodialog1,takenotes,andanswerthequestionsbelow.1.WhataretheaimsoftheNoiseControlClub?2.Whatkindsofnoisearementioned?3.WhatwilltheNoiseControlClubdotohelppeopleunderstandeachotherbetter?First,toraisethepublic'sawarenessofnoisepollution;andsecond,tofindsolutionstoit.Squaredancingandtalkingloudlyonthecellphoneinthebusorinthetrain.They'llraisemoneytomakepostersandinformationsheetsforthepublic.Listentodialog2andfillinthemissingwordsorphrasesaccordingtowhatyouhaveheard.A:Hi,guys!WelcometoourNoiseControlClub!Pleasejoinustocontrolthenoiseinourlife.B:Whatdoyoumeanby“controlnoiseinourlife”?A:Imeannoiseisharmfultoour(1)

.B:Oh,really?A:Ifyoukeeplisteningtoloudmusic,itmaydamageyour(2)

.B:Well,Iseealotofyoungpeoplewearthe(3)

allthetime.A:Thedoctorsayspeopleundertheageof(4)

areverylikelytoexperiencethe(5)

intheirhearing.Ifwedon'ttreatitseriously,wewillslowlylosehearingability.Soweshouldraisethe(6)

fortheneedtoprotectourears.B:That'sa(7)

thingtodo.HowcanIjoinyourclub?A:It'seasy.Please(8)

uphereonthislist,andleaveyourphonenumber,andemail.Wewillgetintouchwithyousoon.healthhearingabilityearphones35damagepublicawarenessmeaningfulsignWorkinsmallgroupstotesthowsoundtravels.Carryouttheexperiment,andthendescribetheresults,andwritethefindingsofyourgroup.Youwillneedacellphone，threecardboardpapertoweltubes，scissors，andatowel.Methods:1.Placethecellphoneaboutafootawayfromyourgroupandcoveritwithatoweltomutethesoundalittle.2.Turnthemusicplayeronandlistentothemusic.3.Putapapertoweltubetoyourearandlisten.4.Nowlengthenyourlisteningtubebyaddingmorepapertoweltubestoit.Questionsforyoutothinkabout:1.Didyounoticeadifferencewhenyouputonetubetoyourearversuslisteningtothemusicplayerwithoutanytubestoyourear?

2.Diditmakeadifferencehowlongyourtubewas?

3.Whatisthetubingdoingtothesound?

Results:

Conclusions:Yes.Whenweputtubestoourear,themusicsoundslouderthanwithoutanytubes.Yes.Thelongerthetube,thelouderthesound.Thetubinghelpstocollectsounds.Themusicsoundslouderthroughatubethanthroughyourear.Andthesoundismuchlouderwhenthetubeislengthened.Thetubehelpstocollectthesoundandtheairinthetubeissetuptovibrateinresonancewiththemusic.DiscussthetopicWhatisthesoundlike