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TheStrawOboeDeterminethefrequencyofastraw
AmathandscienceactivityMaterials:Scissors,ruler,tape,strawsMakingyourstrawoboe:Useyourteethorfingerstoflattenabout2cmatoneendofthestraw.Cuttwo,small,angularcutsoneachsideoftheflattenedend.Itlookslikeaducksbeakandiscalledareed.
Todoandnotice:Putthereedendofthestrawinyourmouth.Positionthereedjustinsideyourlipsandapplylightpressureonthestraw.Blowthroughthestraw,youshouldfeelthereedvibratingonyourlips.Youmayneedtomakeadjustmentswiththestrawtomakethesound.Trymakingasinglepitchwhenblowingthroughthestraws.Explore:Cutseveraldifferentlengthsofstraw;remembertocutthereedoneachone.Blowthrougheachoneandnoticethedifferentsounds.Whatistherelationshipbetweenthelengthofthestrawandthesoundyouhear?
Calculatingthefrequencyofyourstraws.Part1
1. Measurethelengthofyourstrawincentimetersandconverttometers.Ex:23.3cm=.233m(length)
2. Wehavealreadymeasuredthespeedofsound–Activity–Soundtravels.Thespeedofsound=distance/time.
3. Dividethespeedofsoundbythelength.(330-345m/s)4. Example:345m/s÷.233m=1480vibrationspersecond,orHertz.
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TablePart1
Calculatingthefrequencyofstraws.
Makestrawoboesthataredouble,half,quarterlengthsofoneofthestrawoboesusedinPart1.Measureeachoneandcompletethetablebelow.
TablePart2Note Frequency(Hz) Wavelength(cm) Speedofsound~345m/s Usingthechartprovided“PhysicsofMusic–Notes”findthemusicalnoteforeachofthestrawoboes.Eachofthestrawsshouldbeanoctaveofthefirstlength.Whenthelengthisdoubledorcutinhalfitisstillthesamenote,justanoctavehigherorlowerinpitch.Yourstrawoboesfrequencymaynotbeexactlythesameasthechart,findthefrequencythatistheclosest.What’sgoingon?Firstofall,whatissound?Thevibrationofobjectsproducessounds.Thepushandpullonairmolecules,changestheairpressure.Pushesarecompressingairandpullsareseparatingair,rarefactions.Whenyoublowintothereedandgetitvibrating,yousendpulsesofcompressedairdownthestraw,causingtheairinthestrawtostartvibratingtoo.Affectedbythelengthofthestraw,thisvibratingairinturnaffectsthereed’svibrations.Whenthereedvibratesatjusttherightfrequency,theairinthestrawvibratespowerfullyandyouhearaloud
Note Frequency(Hz) Wavelength(cm) Speedofsound~345m/s
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sound,sortoflikeanoboe.Whenthelengthofthestrawchangesthesoundorpitchchanges.Pitchishowhighorlowasoundisperceived.Wemade4differentlengthstrawswithdifferentpitches.Thelongerthestrawthelowerthepitch–theshorterthestrawthehigherthepitch.LIGOconnection:NoiseisLIGO’sbiggestchallenge.Soundisavibration.Vibrationsareallaroundus.Somewecanhearandfeel,otherwecannot.Earthquakesfromallovertheworld,wavescrashingonshoresandwindspushingonbuildingsandtrees,allmovethegroundunderneathLIGO.LIGOisthemostsensitivemeasuringdeviceintheworldandisaffectbyallofthesenoises.Formoreideasandinformationvisitthefollowingwebsite:ScienceBuddiesStaff.“Do-Re-MiwithStraws”ScienceBuddies.ScienceBuddies,7May2015.Web.6June2017http://www.sciencebuddies.org/science-fair-projects/project_ideas/Music_p016.shtmlKathyHolt–June6,[email protected]
Notesanddiagrams
