Q&A
GET T Y IMAGES X2 ILLUSTRATION: DAN BRIGHT
WHATYOU’LL
NEED
■Paper
■Twoicelolly
sticks
■Onewide
rubberband
■Fourthinrubber
bands
■Scissors
WHAT’SHAPPENING
Blowingintotheharmonicamakesthewide
rubberbandvibrate,causingtheairparticles
aroundit tovibrateatthesamefrequency(you
canalsofeelthevibrationswithyourfingertips).
Thesevibrationspassfromairmoleculetoair
molecule,producinga wavethattravelsaway
fromtheharmonica.Whenthiswavereachesyour
ears,youdetectit assound.
Theharmonica’spaperdividersseparatethe
rubberbandintothreedifferentlengths.Blowing
throughthe‘holes’betweenthedividersproduces
differentnotesbecausethedifferentlengthsof
rubbervibrateatdifferentfrequencies.The
frequencyatwhicha rubberbandvibratesis
proportionaltohowtightlyit is stretched,and
inverselyproportionaltohowlongit is andhow
heavyit is.Thismeansthatshorterlengthsof
rubbervibrateata higherfrequency,producinga
higherpitchednote.Blowingharderdoesn’t
changethepitchofthe notes, but should make
them louder.AS
WHATTODO
1.Cutoutfourpaperrectangles,eachroughly4cmx 1cm.
2.Foldeachpieceofpaperinhalfdownitslengththree times to give four
foldedpiecesofpaper,eachroughly0.5cmx 1cm.
3.Stretchthewiderubberbandaroundthelengthofoneofthelollysticks.
4.Placeonefolded piece of paper on top of the rubber band at one end
ofthestick.
5.Putthesecondstickon top so that the piece of paper is sandwiched
betweenthesticks.
6.Cutoffanypaperstickingoutfrombetweenthesticks.
7.Wrapa thinelasticband around the paper and sticks so that the paper is
heldfirmlyinplace.
8.Placea secondpieceofpaperbetweenthesticks,about1cmalongfrom
thefirstpieceofpaper.Again,cutoffany paper sticking out, and secure the
paperinplacewithanelasticband.
9.Repeatwitha thirdpieceofpaperplacedabout2cmfurtheralong.
10.Repeatwitha finalpieceofpaperplacedrightattheotherendofthesticks.
11.Holdtheharmonicasothattherubberbandis aroundthebottomstickand
blowthroughthegaps between the paper dividers. You should get three
different notes!
DIY
SCIENCE
RUBBER BAND HARMONICA
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