超聲波測(cè)距外文文獻(xiàn)加中文翻譯畢業(yè)設(shè)計(jì)

附錄A英文原文ULTASONICRANGINGINAIRG.E.RudashevskiandA.A.GorbatovUDC534,321.9:531.71.083.7Oneofthemostimportantproblemsininstrumentationtechnologyistheremote,contactlessmeasurementofdistancesintheorderof0.2to10minair.Suchaproblemoccurs,forinstance,whenmeasuringtherelativethreedimensionalpositionofseparatemachinemembersorstructuralunits.Interestingpossibilitiesforitssolutionareopenedupbyutilizingultrasonicvibrationsasaninformationcarrier.Thephysicalpropertiesofair,inwhichthemeasurementsaremade,permitvibrationstobeemployedatfrequenciesupto500kHzfordistancesupto0.5mbetweenamemberandthetransducer,orupto60kHzwhenrangingonobstacleslocatedatdistancesupto10m.Ultrasonicwaveproduction:Thesoundwaveistheobjectmechanicalvibrationscondition(orenergy)disseminationform.Theso-calledvibrationisreferstomaterialtheparticlethereciprocatingmotionwhichcarriesonnearbyitspositionofequilibrium.Forexample,drumsurfaceafterrap,itonhighandlowvibrates,thiskindofvibrationalstatetodisseminatesinalldirectionsthroughtheairmedium,thisisasoundwave.Theultrasonicwaveisreferstothevibrationalfrequencytobebiggerthanabove20KHz,itseachsecondvibrationnumberoftimes(frequency)veryhigh,hassurpassedthepersonearsenseofhearingupperlimit(20000Hz),peoplesoundwavenamedultrasonicwavewhichcannothearthiskind.SupersonicandmayWenShengbeessentiallyconsistent,theircommongroundisonekindofmechanicalvibrations,usuallywilldisseminatebythelongitudinalwavewayintheelasticmedium,willbeonekindofenergydisseminationform,itsdiversitywillbetheultrasonicfrequencyishigh,thewavelength,willhavethegoodbeamincertaindistancealongthestraightlinedisseminationandthedirectivity,atpresenttheabdomensupersonicimageformationwillusethefrequencyrangein2~5MHz,(willvibrate1timefor3~3.5MHzeachsecondis1Hz,1MHz=106Hzcommonlyused,namelyeachsecondwillvibrate1,000,000times,butWenBofrequencybetween16-20000HZ).Twomainparametersaboutultrasonicwave:Twomainparametersaboutultrasonicwaveare:Frequency:F≥20KHz;Powerdensity:p=emissivepower(W)/emittingarea(cm2);Usuallyp≥0.3w/cm2;Thesupersonicwaveenergywhichdisseminatesintheliquidcarriesonthecleantotheobjectsurface'scontamination,itsprincipleavailable“thecavitation”thephenomenonexplained:Theultrasonicwavevibrationdisseminateswhentheliquidthesoundwaveintensityofpressurewhichachievesanatmosphericpressure,itspowerdensityis0.35w/cm2,bynowtheultrasonicwavesoundwaveintensityofpressurepeakvaluemightachievethevacuumorthenegativepressure,butinfactdoesnothavethenegativepressureexistence,thereforehasaverytremendouspressureintheliquid,becomestheemptycavitationnucleustheliquidmembertensionfracture.Thiscavityveryclosevacuum,itwhentheultrasonicwaveintensityofpressureachievesreverseisbiggestbursts,asaresultofburststheintenseimpactwhichproducestohittheobjectsurfacecontamination.Thiskindtheshock-wavephenomenonwhichproducesbytheinnumerabletinycavitationairbubblecollapseiscalled“thecavitation”thephenomenon.Thefunctionofultrasonicwave:Theglasscomponents,theglassandceramicarticle'sremovingdirtystuffisterriblebusiness,ifputsinthesegoodsinthecleaningliquid,passesovertheultrasonicwaveagain,onthecleaningliquidfiercevibrationimpactgoodsdirt,cancleancleanlyveryquickly.Althoughsaidthatthehumanitydoesnotlistentothefavorablebalanceoftradesoundwave,butmanyanimalsactuallyhavethisability.Theymayusingtheultrasonicwave“theguidance”,capturefood,oravoidsthedanger.Everybodypossiblysawsummer'snighthashadmanybatsbackandforthtosoarinthegarden,whyhaven'ttheyintheluminoussituationsoared,butwillnotlosethedirection?Thereasonisthebatcansendout2~100,000hertzultrasonicwaves,thisisjustlikeisaactivity“theradarstation”.Thebatispreciselyusesthiskind“theradar”frontthejudgmentflightisaninsect,perhapsobstacle.Butradar'squalityhasseveraldozens,severalhundred,severalthousandkilograms,butinsomeimportantperformanceprecision.Antijammingabilityandsoon,batfarsuperiorandmodernwirelessbeacon.Onthedeepresearchanimalbodyeachkindoforgan'sfunctionandthestructure,willobtaintheknowledgeusesfortoimprovetheexistingequipment,thisisanewdisciplinewhichforthepastmanyyearsdevelops,thenamedbionics.OurhumanityonlythentheacademicsocietyusestheultrasonicwaveuntiltheFirstWorldWar,thisisuses“thesoundnavigationandranging”theprinciplesearchesinthesoundingthegoalandthecondition,likesubmarine'spositionandsoon.Thistimethepeoplesendoutaseriesofdifferentfrequenciestothewaterintheultrasonicwave,thentherecordandtheprocessingreflectionecho,wethenmayestimatethesurveyfromtheechocharacteristicthedistance,theshapeandthedynamicchange.Inthemedicineusingtheultrasonicwavewasmostearlyin1942,AustrianDr.DuSieckusesthesupersonictechnologytoscanthebrainstructureforthefirsttime;Startedlatertothe60sdoctorstheultrasonicwavetoapplyintheabdomenorgan'ssurvey.Nowtheultrasonicwavescanningtechniquehasbecomethemodernmedicinetodiagnosetheessentialtool.Themedicineultrasonicwaveinspection'sprincipleofworkandthesoundnavigationandranginghavecertainsimilarity,soontheultrasonicwavelaunchesinthehumanbody,whenitmeetsthecontactsurfacewheninvivowilloccurreflectsandrefracts,andispossiblyabsorbedintheBodytissueweakens.Becausethehumanbodyeachkindoforganization'sshapeandthestructurearenotsame,thereforeitsreflectionandtherefractionaswellastheabsorptionultrasonicwave'sdegreeisalsodifferent,doctorsarepreciselyreflectedthroughtheinstrumentthewavemode,thecurve,orthephantomcharacteristicdistinguishesthem.Inadditionrecombinationanatomyknowledge,normalandpathologychange,thenmaydiagnosetheorganwhichinspectswhethertobesick.Atpresent,doctorsapplytheultrasounddiagnosismethodhasthedifferentform,maydivideintoA,B,MandtheDfourbroadheadings.A:Bytheprofiledemonstratedthattheorganizationcharacteristicthemethod,mainlyusesinsurveyingorgan'sdiameteralwire,determinesitssize.Mayuseforsomephysicalpropertywhichdistinguishesthepathologicalchangetoorganize,likesubstantive,liquidperhapsgaswhethertohaveandsoon..B:Withplanefigure'sformdemonstratedthatisinvestigatedorganization'sspecialdetails.Wheninspection,firsttransformsthehumanbodycontactsurface'sreflectionsignalintothestrongandtheweakdifferentluminousspot,theseluminousspotsmaycomeoutthroughthefluorescentscreenappearance,thismethodintuitiveisgood,duplicated,maycontrastforaround,thereforewidelyusesinsystemdisease'sandsoongynecologyandobstetricsdepartment,uropoiesis,digestionandcardiovasculardiagnoses.M:Usedinobservingtheactivecontactsurfacetimevariationonemethod.Mostissuitableininspectingheart'sactivesituation,itscurve'sdynamicchangeiscalledtheechocardiogram,mayusefortoobservehearteachstructuretheposition,theactivestate,thestructureconditionandsoon,usesintheaccessoryheartandthetrunkepidemicdisease'sdiagnosis.D:Usedfortoexaminethebloodflowandtheorganactivityoneultrasounddiagnosismethodspecially,isalsocalledtheDopplersupersonicdiagnosticmethod.Maydeterminethatthebloodvesseliswhetherunobstructed,thelumenwhetherornotnarrow,unenlightenedaswellasthepathologicalchangespot.Newgeneration'sDultrasonicwavecanalsointhequotadeterminationlumenblood'scurrentcapacity.InthelastfewyearsthescientisthasdevelopedthecolorcodingDopplersystem,mayundertheechocardiogramdissectionsymbolinstruction,bythedifferentcolordemonstrationbloodstreamdirection,thelusterdepthrepresentthebloodstreamthespeedofflow.Nowalsohasthethree-dimensionalultrasonoscopy,supersonicCT,thesupersonicendoscopeandsoonsupersonictechnologytoemergeunceasingly,andmayalsowithothermonitoringdeviceunionuse,makedisease'sdiagnosisrateofaccuracytoenhancegreatly.Theultrasonicwavetechnologymedicalarenaisplayingthehugerole,alongwiththescienceprogress,itwillbemoreperfect,willbenefitwellthehumanity.Theproblemofmeasuringdistancesinairissomewhatdifferentfromotherproblemsinthea-pplicationofultrasound.Althoughthepossibilityofusingacousticrangingforthispurposehasbeenknownforalongtime,andatfirstglanceappearsverysimple,neverthelessatthepresenttimethereareonlyasmallnumberofdevelopmentsusingthismethodthataresuitableforpracticalpurposes.Themaindifficultyhereisinprovidingareliableacousticthree-dimensionalcontactwiththetestobjectduringseverechangesintheair'scharacteristic.Practicallyallacousticarrangementspresentlyknownforcheckingdistancesuseamethodofmeasuringthepropagationtimeforcertaininformationsamplesfromtheradiatortothereflectingmemberandback.Theunmodulatedacoustic(ultrasonic)vibrationsradiatedbyatransducerarenotinthemselvesasourceofinformation.Inordertotransmitsomeinformationalcommunicationthatcanthenbeselectedatthereceivingendafterreflectionfromthetestmember,theradiatedvibrationsmustbemodulated.Inthiscasetheultrasonicvibrationsarethecarrieroftheinformationwhichliesinthemodulationsignal,i.e.,theyarethemeansforestablishingthespatialcontactbetweenthemeasuringinstrumentandtheobjectbeingmeasured.Thisconclusion,however,doesnotmeanthattheanalysisandselectionofparametersforthecarriervibrationsisofminorimportance.Onthecontrary,thefrequencyofthecarriervibrationsislinkedinaveryclosemannerwiththecodingmethodfortheinformationalcommunication,withthepassbandofthereceivingandradiatingelementsintheapparatus,withthespatialcharacteristicsoftheultrasoniccommunicationchannel,andwiththemeasuringaccuracy.Letusdwellonthequestionsofgeneralimportanceforultrasonicranginginair,namely:onthechoiceofacarrierfrequencyandtheamountofacousticpowerreceived.Ananalysisshowsthatwithconicaldirectivitydiagramsfortheradiatorandreceiver,andassumingthatthedistancebetweenradiatorandreceiverissubstantiallysmallerthanthedistancetotheobstacle,theamountofacousticpowerarrivingatthereceivingareaPrforthecaseofreflectionfromanidealplanesurfacelocatedatrightanglestotheacousticaxisofthetransducercomestowherePradistheamountofacousticpowerradiated,Bistheabsorptioncoefficientforaplanewaveinthemedium,Listhedistancebetweentheelectroacoustictransducerandthetestme-mber,disthediameteroftheradiator(receiver),assumingtheyareequal,andc~istheangleofthedirectivitydiagramfortheelectroacoustictransducerintheradiator.BothinEq.(1)andbelow,theabsorptioncoefficientisdependentontheamplitudeandnotontheintensityasinsomeworks[1],andthereforewethinkitnecessarytostressthisdifference.Inthevariousproblemsofsoundrangingonthetestmembersofmachinesandstructures,therelationshipbetweenthesignalattenuationsduetotheabsorptionofaplanewaveandduetothegeometricalpropertiesofthesoundbeamare,asarule,quitedifferent.Itmustbepointedoutthatthechoiceofthegeometricalparametersforthebeaminspecificpracticalcasesisdictatedbytheshapeofthereflectingsurfaceanditsspatialdistortionrelativetosomeaverageposition.Letusconsiderinmoredetailtherelationshipbetweenthegeometricandthepowerparametersofacousticbeamsforthemostcommoncasesofrangingonplaneandcylindricalstructuralmembers.ItiswellknownthatthedirectionalcharacteristicWofacircularpistonvibratinginaninfinitebaffleisafunctionoftheratioofthepiston'sdiametertothewavelengthd/λasfoundfromthefollowingexpression:(2)whereJlisaBesselfunctionofthefirstorderandαistheanglebetweenanormaltothepistonandalineprojectedfromthecenterofthepistontothepointofobservation(radiation).FromEq.(2)itisreadilyfoundthatatwo-to-onereductioninthesensitivityofaradiatorwithrespecttosoundpressurewilloccurattheangle（3）Foranglesα≤20.Eq.(3)canbesimplifiedto（4）wherecisthevelocityofsoundinthemedimaaandfisthefrequencyoftheradiatedvibrations.ItfollowsfromEq.(4)thatwhenradiatingintoairwherec=330m/sec,thenecessarydiameteroftheradiatorforaspedfiedangleofthedirectivitydiagramatthe0.5levelofpressuretakenwithrespecttotheaxiscanbefoundtobe（5）wheredisincm,fisinkHz,andαisindegreesofangle.CurvesareshowninFig.1plottedfromEq.(5)forsixanglesofaradiator'sdirectivitydiagram.Thedirectivitydiagrmneededforaradiatorisdictatedbythemaximumdistancetobemeasuredandbythespatialdispositionofthetestmemberrelativetotheotherstructuralmembers.Inordertoavoidtheincidenceofsignalsreflectedfromadjacentmembersontotheacousticreceiver,itisnecessarytoprovideasmallangleofdivergenceforthesoundbeamand,asfaraspossible,asmall-diameterradiator.Thesetworequirementsaremutuallyinconsistentsinceforagivenradiationfrequencyareductionofthebeam'sdivergenceanglerequiresanincreasedradiatordiameter.Infact,thediameterofthe"sonicated"spotiscontrolledbytwovariables,namely:thediameteroftheradiatorandthedivergenceangleofthesoundbeam.Inthegeneralcasetheminimumdiameterofthe"sonicated"spotDminonaplanesurfacenormallydisposedtotheradiator'saxisisgivenby（6）whereListheleastdistancetothetestsurface.ThespecifiedvalueofDmincorrespondstoaradiatorwithadiameter（7）AsseenfromEqs.(,6)and(7),theminimumdiameterofthe"sonieated"spotatthemaximumrequireddistancecannotbelessthantworadiatordiameters.Naturally,withshorterdistancestotheobstaclethesizeofthe"sonicated"surfaceisless. LetusconsiderthecaseofsoundrangingonacylindricallyshapedobjectofradiusR.TheproblemistomeasurethedistancefromtheelectroacoustictransducertothesidesurfaceofthecylinderwithitsvariouspossibledisplacementsalongtheXandYaxes.Thenecessaryangleαoftheradiator'sdirectivitydiagramisgiveninthiscasebytheexpression（8）whereαisthevalueoftheangleforthedirectivitydiagram,Ymaxisthemaximumdisplacementofthecylinder'scenterfromtheacousticaxis,andLministheminimumdistancefromthecenteroftheelectroacoustictransducertothereflectingsurfacemeasuredalongthestraightlineconnectingthecenterofthememberwiththecenterofthetransducer.Itisclearthatwhenmeasuringdistance,the"running"timeoftheinformationsignaliscontrolledbythelengthofthepathinadirectionnormaltothecylinder'ssurface,orinotherwords,themeasuredistanceisalwaystheshortestone.Thisstatementiscorrectforallcasesofspecularreflectionofthevibrationsfromthetestsurface.ThesimultaneoussolutionofEqs.(2)and(8)whenW=0.5leadstothefollowingexpression:(9)Intheparticularcasewherethesoundrangingtakesplaceinairhavingc=330m/sec,andontheasstunptionthatLmin<<R,thenecessarydiameterofaunidirectionalpistonradiatordcanbefoundfromthefomula(10)wheredisincmandfisinkHz.CurvesareshowninFig.2fordeterminingthenecessarydiameteroftheradiatorasafunctionoftheratioofthecylinder'sradiustothemaximumdisplacementfromtheaxisforfourradiationfrequencies.AlsoshowninthisfigureisthedirectivitydiagramangleasafunctionofRandYrnaxforfourratiosofminimumdistancetoradius.Theultrasonicabsorptioninairisthesecondfactorindeterminingtheresolutionofultrasonicrangingdevicesandtheirrangeofaction.Theresultsofphysicalinvestigationsconcerningthemeasurementofultrasonicvibrationsairaregivenin[1-3].Upuntilnowtherehasbeennounambiguousexplanationofthediscrepancybetweenthetheoreticalandexpe-rimentalabsorptionresultsforultrasonicvibrationsinair.Thus,forfrequenciesintheorderof50to60kHzatatemperatureof+25oCandarelativehumidityof37%theenergyabsorptioncoefficientforaplanewaveisabout2.5dB/mwhilethetheoreticalvalueis0.3dB/m.TheabsorptioncoefficientBasafunctionoffrequencyforatemperatureof+25oCandahumidityof37%accordingtothedatain[2]canbedescribedbyTable1.Theabsorptioncoefficientdependsontherelativehumidity.Thus,forfrequenciesintheorderof10to20kHzthehighestvalueoftheabsorptioncoefficientoccursat20%humidity[3],andat40%humiditytheabsorptionisreducedbyabouttwotoone.Forfrequenciesintheorderof60kHzthemaximumabsorptionoccursat30.7ohumidity,droppingwhenitisincreasedto98%orloweredto10%byafactorofapproximatelyfourtoone.Theairtemperaturealsohasanappreciableeffectontheultrasonicabsorption[1].Whenthetemperatureofthemediumisincreasedfrom+10to+30,theabsorptionforfrequenciesbetween30and50kHzincreasesbyaboutthreetoone.Takingallthefactorsnotedaboveintoaccountwearriveatthefollowingapproximatevaluesfortheabsorptioncoefficient:atafrequencyof60kHz/3min=0.15m-1and~max=0.5-1;atafrequencyof200kHz/~min=0.6m-1andBmax=2m-1.TherelationshipsunderconsiderationareshowngraphicallyinFig.3.Intheupperpartofthediagramcurvesofg=f(L)areplottedforfivevaluesofthetotalangleintheradiator'sdirectivitydiagram,where（11）Thevaluesfortheminimum~minandrnaxil-num~max"transmittance"coefficientswereobtainedintheabsenceofaerosolsandrain.Theirdifferenceistheresultofthepossiblevariationsintemperatureovertherangefrom-30to+50~andinrelativehmnidityovertherangefrom10to98%.Theoverallvalueofthe"transmittance"isobtainedbymultiplyingthevaluesofgand0forgivenvaluesofL,f,andd.LITERATURECITED1.L.Bergman,Ultrasonics[Russiantranslation],Izd.Inostr.Lit.,Moscow(1957).2.V.A.Krasil'nikov,SonicandUltrasonicWaves[inRussian],Fizmatgiz,Moscow(1960).3.M.MokhtarandE.Richardson,ProceedingsoftheRoyalSociety,184(1945).附錄B中文翻譯在空氣中超聲測(cè)距G.E.RudashevskiandA.A.GorbatovUDC534,321.9:531.71.083.7在儀器技術(shù)中遠(yuǎn)程是最重要的一個(gè)問題。在空氣中，從0.2米至10米非接觸式測(cè)量距離時(shí)，涉及到了這個(gè)問題，例如，在測(cè)量時(shí)個(gè)別機(jī)件或結(jié)構(gòu)單位的相對(duì)三維位置。有趣的是，是利用超聲振動(dòng)作為信息運(yùn)輸工具，開啟了解決辦法的可能性.在空氣這個(gè)自然道具中，進(jìn)行測(cè)量的是雇用成員和傳感器之間距離0.5米的時(shí)候，允許振動(dòng)頻率高達(dá)500千赫，或當(dāng)與障礙物之間修正距離延伸達(dá)10米時(shí)候，振動(dòng)頻率高達(dá)60千赫茲。超聲波的產(chǎn)生：聲波是物體機(jī)械振動(dòng)狀態(tài)（或能量）的傳播形式。所謂振動(dòng)是指物質(zhì)的質(zhì)點(diǎn)在其平衡位置附近進(jìn)行的往返運(yùn)動(dòng)。譬如，鼓面經(jīng)敲擊后，它就上下振動(dòng)，這種振動(dòng)狀態(tài)通過空氣媒質(zhì)向四面八方傳播，這便是聲波。超聲波是指振動(dòng)頻率大于20KHz以上的,其每秒的振動(dòng)次數(shù)（頻率）甚高，超出了人耳聽覺的上限（20000Hz），人們將這種聽不見的聲波叫做超聲波。超聲和可聞聲本質(zhì)上是一致的，它們的共同點(diǎn)都是一種機(jī)械振動(dòng)，通常以縱波的方式在彈性介質(zhì)內(nèi)會(huì)傳播，是一種能量的傳播形式，其不同點(diǎn)是超聲頻率高，波長(zhǎng)短，在一定距離內(nèi)沿直線傳播具有良好的束射性和方向性，目前腹部超聲成象所用的頻率范圍在2~5MHz之間，常用為3~3.5MHz（每秒振動(dòng)1次為1Hz，1MHz=106Hz，即每秒振動(dòng)100萬次，可聞波的頻率在16－20000HZ之間）。超聲波的兩個(gè)主要參數(shù)：超聲波的兩個(gè)主要參數(shù)：頻率：F≥20KHz；功率密度：p=發(fā)射功率(W)/發(fā)射面積(cm2)；通常p≥0.3w/cm2；在液體中傳播的超聲波能對(duì)物體表面的污物進(jìn)行清洗，其原理可用“空化”現(xiàn)象來解釋：超聲波振動(dòng)在液體中傳播的音波壓強(qiáng)達(dá)到一個(gè)大氣壓時(shí)，其功率密度為0.35w/cm2，這時(shí)超聲波的音波壓強(qiáng)峰值就可達(dá)到真空或負(fù)壓，但實(shí)際上無負(fù)壓存在，因此在液體中產(chǎn)生一個(gè)很大的壓力，將液體分子拉裂成空洞一空化核。此空洞非常接近真空，它在超聲波壓強(qiáng)反向達(dá)到最大時(shí)破裂，由于破裂而產(chǎn)生的強(qiáng)烈沖擊將物體表面的污物撞擊下來。這種由無數(shù)細(xì)小的空化氣泡破裂而產(chǎn)生的沖擊波現(xiàn)象稱為“空化現(xiàn)象”。超聲波的作用：玻璃零件.玻璃和陶瓷制品的除垢是件麻煩事，如果把這些物品放入清洗液中，再通入超聲波，,清洗液的劇烈振動(dòng)沖擊物品上的污垢，能夠很快清洗干凈。雖然說人類聽不出超聲波，但不少動(dòng)物卻有此本領(lǐng)。它們可以利用超聲波“導(dǎo)航”、追捕食物，或避開危險(xiǎn)物。大家可能看到過夏天的夜晚有許多蝙蝠在庭院里來回飛翔，它們?yōu)槭裁丛跊]有光亮的情況下飛翔而不會(huì)迷失方向呢？原因就是蝙蝠能發(fā)出2～10萬赫茲的超聲波，這好比是一座活動(dòng)的“雷達(dá)站”。蝙蝠正是利用這種“雷達(dá)”判斷飛行前方是昆蟲，或是障礙物的。而雷達(dá)的質(zhì)量有幾十，幾百，幾千千克，而在一些重要性能上的精確度?？垢蓴_能力等，蝙蝠遠(yuǎn)優(yōu)與現(xiàn)代無線電定位器.深入研究動(dòng)物身上各種器官的功能和構(gòu)造，將獲得的知識(shí)用來改進(jìn)現(xiàn)有的設(shè)備，這是近幾十年來發(fā)展起來的一門新學(xué)科，叫做仿生學(xué)。我們?nèi)祟愔钡降谝淮问澜绱髴?zhàn)才學(xué)會(huì)利用超聲波，這就是利用“聲納”的原理來探測(cè)水中目標(biāo)及其狀態(tài)，如潛艇的位置等。此時(shí)人們向水中發(fā)出一系列不同頻率的超聲波，然后記錄與處理反射回聲，從回聲的特征我們便可以估計(jì)出探測(cè)物的距離、形態(tài)及其動(dòng)態(tài)改變。醫(yī)學(xué)上最早利用超聲波是在1942年，奧地利醫(yī)生杜西克首次用超聲技術(shù)掃描腦部結(jié)構(gòu)；以后到了60年代醫(yī)生們開始將超聲波應(yīng)用于腹部器官的探測(cè)。如今超聲波掃描技術(shù)已成為現(xiàn)代醫(yī)學(xué)診斷不可缺少的工具。醫(yī)學(xué)超聲波檢查的工作原理與聲納有一定的相似性，即將超聲波發(fā)射到人體內(nèi)，當(dāng)它在體內(nèi)遇到界面時(shí)會(huì)發(fā)生反射及折射，并且在人體組織中可能被吸收而衰減。因?yàn)槿梭w各種組織的形態(tài)與結(jié)構(gòu)是不相同的，因此其反射與折射以及吸收超聲波的程度也就不同，醫(yī)生們正是通過儀器所反映出的波型、曲線，或影象的特征來辨別它們。此外再結(jié)合解剖學(xué)知識(shí)、正常與病理的改變，便可診斷所檢查的器官是否有病。目前，醫(yī)生們應(yīng)用的超聲診斷方法有不同的形式，可分為A型、B型、M型及D型四大類。A型：是以波形來顯示組織特征的方法，主要用于測(cè)量器官的徑線，以判定其大小。可用來鑒別病變組織的一些物理特性，如實(shí)質(zhì)性、液體或是氣體是否存在等。B型：用平面圖形的形式來顯示被探查組織的具體情況。檢查時(shí)，首先將人體界面的反射信號(hào)轉(zhuǎn)變?yōu)閺?qiáng)弱不同的光點(diǎn)，這些光點(diǎn)可通過熒光屏顯現(xiàn)出來，這種方法直觀性好，重復(fù)性強(qiáng)，可供前后對(duì)比，所以廣泛用于婦產(chǎn)科、泌尿、消化及心血管等系統(tǒng)疾病的診斷。M型：是用于觀察活動(dòng)界面時(shí)間變化的一種方法。最適用于檢查心臟的活動(dòng)情況，其曲線的動(dòng)態(tài)改變稱為超聲心動(dòng)圖，可以用來觀察心臟各層結(jié)構(gòu)的位置、活動(dòng)狀態(tài)、結(jié)構(gòu)的狀況等，多用于輔助心臟及大血管疫病的診斷。D型：是專門用來檢測(cè)血液流動(dòng)和器官活動(dòng)的一種超聲診斷方法，又稱為多普勒超聲診斷法?？纱_定血管是否通暢、管腔有否狹窄、閉塞以及病變部位。新一代的D型超聲波還能定量地測(cè)定管腔內(nèi)血液的流量。近幾年來科學(xué)家又發(fā)展了彩色編碼多普勒系統(tǒng)，可在超聲心動(dòng)圖解剖標(biāo)志的指示下，以不同顏色顯示血流的方向，色澤的深淺代表血流的流速?，F(xiàn)在還有立體超聲顯象、超聲CT、超聲內(nèi)窺鏡等超聲技術(shù)不斷涌現(xiàn)出來，并且還可以與其他檢查儀器結(jié)合使用，使疾病的診斷準(zhǔn)確率大大提高。超聲波技術(shù)正在醫(yī)學(xué)界發(fā)揮著巨大的作用，隨著科學(xué)的進(jìn)步，它將更加完善，將更好地造福于人類。應(yīng)用超聲波在空氣中測(cè)量距離不同于其他的問題。雖然能否利用聲波修正測(cè)距的可行性已經(jīng)研究了很長(zhǎng)一段時(shí)間，乍一看似乎很簡(jiǎn)單，但是目前只有為數(shù)不多的新發(fā)明使用這種適合實(shí)際目的方法，主要困難是在有嚴(yán)重特有變化的空氣中提供一個(gè)可靠試驗(yàn)對(duì)象去接觸三維聲波。幾乎所有的目前已知用來校驗(yàn)距離使用的，都是為了某些來自用來反射成員和后面的散熱器信息樣本，測(cè)量傳播時(shí)間解決聲音的辦法。該未解調(diào)的聲（超聲）振動(dòng)由傳感器輻射的，本身并不是一個(gè)信息來源.在接收端，來自測(cè)試會(huì)員反射后，為了傳遞一些情報(bào)信息，因而被選定后，輻射振動(dòng)一定會(huì)被調(diào)制。在這種情況下，超聲波振動(dòng)是在于調(diào)制信號(hào)的信息的承運(yùn)人，即他們就是在測(cè)量?jī)x器和測(cè)量穩(wěn)定的對(duì)象之間建立了空間三維接觸的手段。這一結(jié)論，但是，并不意味著分析和選擇的參數(shù)承運(yùn)人振動(dòng)重要性小.正相反，承運(yùn)人振動(dòng)頻率與信息溝通編碼方法，與接收通頻帶和儀器中的輻射元素，與超聲波空間特有的溝通渠道，以及測(cè)量精度是具有非常密切的聯(lián)系方式。讓我們談具有普遍意義的空氣中超聲波測(cè)距問題，即：載波頻率和的被普遍認(rèn)為標(biāo)準(zhǔn)的聲音數(shù)額的選擇。（1）在Prad輻射聲功率，B是平面波在介質(zhì)中吸收系數(shù)為，L