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Ultrasoundhasmanyothermedicalusestoo，bothintheareasofsg（almosteveryohedevelopedworldisnowsedbeforebirth）a（liketheremovalofdentaltartar，where25kHzsoundisusedinwithawaterjet）.Uhermedicaltreatments，ultrasoudoflinstantly，oftenrequireslow-ology，andusuallyinvolvesminimalpatieiohatultrasouorsarerelativelyportablealeameansthattheybeusedoutsidethehospitale，fromdiathermy（deep-tissueheating）unitsfoundinmanygymstowouionsystems，deployedoosavethelivesofsoldierswhowouldotherwiseperishfrombloodloss.
Ultrasoundhasbeehetreatmentoftumoursofmanykinds—ingotherwiseinoperablebraieiquecalledeitherHIFU（high-iyfocussedultrasound），orHITU（high-iherapeuticultrasound）.Aswellasdestroyiissuesbyheatioabout9ionsaboutthesizeofagrairasoniducedbubbleformationintumourshasbeeomakethemmoresusceptibletochemotherapy.Themaiheuseofultrasouslikethese，whieedpredaccuratetargeting，isthatthepathsoftheultrasoundbeamsdepeiesaiesoftheinterveningbodytissues.So，modelsofbodypartsmadefromartificialtissue-mimigmaterialsareusedtocalibrateandprogrammetheequipment.
Amhtforwarduseofultrasoundihotripsy，inwhichhigh-powerpulsessimplypouou，smashiopiecessmallenoughtopassoutwithurine.
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&hebest-krasoundisthesgoffoetuses.Sihediaphragmofaalloudspeakerovequioughtoproducethemegahertzfrequenciesrequired，apiezoelectricprojectorisusedinstead.Gelisappliedtotheabdomen，sothatthereisnoairlayertoreffectorabsorbthesourasoundwavesbouerfacesbetweehdiflerentimpedances，suusnioticffuid.Hence，bymeasuringpreciselyhowlongittakesforechoestoreturerfagatofthedifleringsouiesiheirpositionsbeworkedout.Bymovingthebeamarouhree-dimensionalmapbecalculated，aoareal-timevideoimage.
&loudspeakers，apiezoelesducerisreciprocal—suppliedwithanosgtitprodudwave，and，versely，whenstruckbyasougeesarial.So，ialsertheserheadactsasboththesourceoftheultrasoundsaoroftheirechoes.
Withveryhigh-frequensrelativelysharpimagesbemade:a1MHz（onemillinalimagedetailsatthemillimetrescale，theexactvaluedependiicpropertiesofthetissuebringviewed，andmanysowgoupto15MHz，or50MHzforeyeandskinsers.
&hisispaltryparedtotheeightbilliedbyanaicroscope，whisequeailsassmallas0.03mifortunately，suchhigh-frequendsareabsorbedbyalmostallmediabeforetheyhavetravelledasire，andtheonlyuseableexisliquidhelium—whichwillboilifcolderthan5kelvin（fi268°C）.Theelaborategsystemsrequiredmeanthataicroscopesarehereasonstheyareusedatallarethattheyprobeuhesurfaples，andthatsomematerialswhicharehardtodistinguishfromtheirsurroundingsvisuallyarehighlyreffectivetosound.
Outsidethemedicalfield，oheodiagnosticapplisofultrasoundisiionofffawsandrailwaylines，foriolocatethese，aseriesofsoundburstsissentaloobetested.Inpulse-eode，thetransmitterandreceiverarepositioher:ifaffawispresent，thepulsesarereffedtheirarrivaltimesiheffawposition.Intransmissioedtransmitterareseparatedandahepulsesintransitihepresenogehetestobject.Thisapproaalsobeusedforthedeterminationofmeicalstressesinsolids:becausetheelastiaterialsalterwheheirsouiesalsogelocally.
Thepowerofultrasonics
Thoughthermaleflectsofhigh-powerultrasoundhavemanyapplis，italsodeliveritsehroughmeicalefleediuThesnappingshrimpprovidesararenaturalexampleoftheuseoftheshodstressesmadebyultrasouhaudiofrequeokill.Theloudandsuddenclickproduthecreaturesnapsitscludesfrequeo200kHz，phtokillorstunbothpreyandwould-bepredatorsalike.
&ilizedbyshrimpsorhumans，themeicalpowerofultrasoundisusuallydeliveredthrough，whichistheformationacollapseoftiallliquidssuchbubbles，madeeitheroftheiroourorofair.Whenthepressureofaliquidfalls，thesebubblesgrow（whichisthecauseressurizederoffizzydrinkisopened）.Sindwaveisasequenceofloressures，
itcausesbubblestoswellandshrinkrapidly，andathighpowersahebubblespulsatesovioleandimplode，suddeheirvibratiyintheformofheat.Thetemperaturesinvolvedmayexceedthoseonthesurfaceofthesun，andmaketheliquidglowwithlight（aphenomenoninesce，ingshrimpalsoinitiate）.
&heenergyappearsonlywithintihebodyofliquiddoesicularlyhot.Buttheburstsofhighlytratedenergybeusedtoinitiatechemiges（sory），aerilizesubmergedobjectssuchasmedistruments.-basedgismosteflethe20te.Athigherfrequerasoundalsocausesagitationofliquids，whiinatesgefletherange100kHzto1MHz.Irasohsusebotheflects.
High-powerultrasound（without）isroutinelyusedforffuxlesssofpriboards，inwhichtheelectricallyheatedtipofasironisvibratedatultrasostillhigherpowers，finewiresbeweldedtogether，heatedfromwithiiorasonicvibratioageofthisisthat，siiisrestrictedtotheinsonified（sound-filled）wires，theultrasouheatupnearbyaerialsareweldedultrasonically;thefrequendependsohepartstobewelded，from60kHzforthesmallestelementsto1est.
High-powerultrasoundbeusedtolevitatesmallobjects.Althoughtheforvolvedarefeeble，inmicrogravityessuchastheinteriorsofspastheycouldbeusedtoholddelistrumentsinpositiassembly，hlyreactivechemiingintotaything.
&erlimits:phonons
&remelyhighfrequendsbehaveinwaysradicallydifferenttothoseearefamiliar:justlikeeleagicradiation，inwhichthehighestfrequenciesbehavemuchmorelikepartiwaves（heheindividualclicksofaGeigerregisteringthepresenarays），thehighest-frequendsbehavelikeparticlescalledphoencewasdisdirectly:bythelate19thtury，itwasknoecifitofheatwasoraisethetemperatureofasubstanedegree.Thespecificheatherthanthatof，say，oil，whisittakeslooboilakettleofwaterthaleofoil.
Gasesandsolidshavespecificheatstoo，butthereuzzlinganomaly:ihetemperatureofasolidtakesabouttwiceasmuergyasraisiureofthesameamountofthesamesubstasgaseousforThismeansthatsolids（aainliquids）musthaveameansheatwhiavailabletogases.Themeismisvibration:amoleasolidoscillatearounditsequilibriumposition，likeapenduluBut，unlikeapendulum，anosgmoleotslowgradually.Thelawsofquantummeithatitmustjumpfromarapidtoaslowos，adoessoittransfersaphononofvibratiytoanothermolecule.Thewaysinwhichsolidsdudelectribeatedforbythebehaviourofphonons.
Infrasound
Asthelowerfrequenanhearingisapproached，theiyofjust-audiblesoundsincreases:apuretoisjustaudibleat20Hzisnearly300milliontimesmorepowerful（allsbeihanajust-audibleto4kHz.Suchpowerfullow-frequendsarerarelyenteredinair，butsolid-borneversionsareorusites，inundergroundstatioorways，andinseismicallyactiveareas，wheretheyeasilybefelt.
Low-poweredairborneinfrasounds，oherhand，surroundusallthetime.Theyareeveedalk:thecyclicairpressuregesatourearsduetoourupanddownheadmovementsstituteaninfrasouaround1Hz.Seawavesgeeinfrasoundsataround0.2Hz.Thelowest-frequenaturalsoundsofallhighintheairanddeepunderground:bothauroraeandvoloesprodufrasoundsataround0.01Hz.
&hekeycharacteristifrasoundisthatittravelfarfurtherthahroughsea，ground，orair;inair，infrasoundsfromthousandsofkilometresaway（made，forexample，byeruptingvoloes）easilybedetected，thoughnotusuallybymies.Justaswefeel，ratherthanhear，infrasound，soweusespecializedbarometerstomeasureit.Infrasoundalsobedetectedbymeauregesitcauses.
Thereisevideinfrasoundhasarasonhumanshertypesofsound，inhaofemotionalresponses:wheofmodernclassicalmusipaniedbyinfrasound，thereeoplewhohatedthemusidfarmorewholovedit，thanataemusioinfrasonient.Otherexperimehatdriversexposedtoinfrasouiredveryquidithaseveedasacauseofsupposedhauntings，partlythroughdirealeffedpartlythroughvibrationoftheeyeball，giviovisualdisturbances.
Infrasoundhasprovedtobeareliablemeaingbolides，whicharemeteoroidsthatexplodeinffight.Siravelsupersonicallythroughtheatmeeinfrasound-risastheyfall.Moreinfrasouedwhenthebolidesexplode.Alltheseairbeesolid-borneversioheyreachtheEarth，andsurfacewavesaremadewhenthebmentscrashtoEarth.Thefrequeiming，andamplitudesofallthesesoundsbiogiveadetailedanalysisofthepath，motiohebolide.
However，infrasoundisusuallyofmorecetouswhehroughtheEarth—andultrasoundreallyesintoitsower.ItistothesemediathatweturninChapter7.
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