Soundvibrationsandwaves

Soundisaformofenergy.Soundsaremadewhenthingsvibrate.Thevibrationsarepassedon

byparticles.Soundthereforeneedsasubstancetopassonthevibrations,soitcantravelthrough solids,liquidsandgasesbutnotthroughavacuum.

.

Thespeedofsoundisfasterthroughmaterialinwhichparticlesareclosertogether.Closerparticles

hiteachothermoreeasilyandsotheenergyismorelikelytobepassedfromoneparticletothe next.Whenthesoundenergymovesfromoneplacetoanotherithasbeentransferred.The

soundenergytravelsinalldirectionsbecausetheparticlesmoveinalldirectionsunlesssomething

stopsthem.

Theoscilloscope


Thefrequencyofasoundwaveisthenumberof

completewavespassingapointeachsecond.Theunit offrequencyishertz(Hz).Thesourceofthesoundis vibratingatthesamenumberofcyclespersecondas thefrequencyofthewaveitmakes.Soundwaveswith

ahighfrequencyproducesoundswithahighpitch.

Thewavelengthisthedistancebetweenanytwoidentical pointsonneighbouringwaves.


Halftheheightofthewaveiscalledtheamplitude.Theloudnessorintensityofasounddepends

ontheamplitudeofthewave.Loudernoteshavemoreenergyandhavewaveswithbigger

amplitudes.

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Hearingandtheear

Soundwavestravelthroughtheairandintotheear.Theycausetheeardrumtovibrate.The vibrationsarepassedontothecochleaintheinnerear,wheretheyarechangedtoelectrical signalscalledimpulses.Anervetakesthismessagetothebrain.Whenthemessagereachesthe brainwehearthesound.

Loudsoundscandamagetheeardrumorthecochlea.Peoplewhoareexposedtoloudsoundsfor longperiodsoftimeareatriskofdamagingtheirhearingorevensufferingpermanentdeafness.

Toavoidthis,peoplewhoworkinloudenvironmentswearearprotection.Unpleasantsoundis oftencallednoise.Wax,earinfectionsandgettingoldercanalsoaffecthearing.

Wecanmeasurehowloudasoundisbyusingasoundintensitymeter.Itmeasurestheloudness

ofasoundindecibels(dB).Thethresholdofhearingisthequietestsoundwecanhearand thisis0dB.

Softmaterialsabsorbsound.Softmaterialsareusedinsoundproofingandformakingear protectors.Thegapbetweentheglassindoubleglazingcontainsfewparticlesandsoisalsoused

forsoundproofing.

Soundandlight

Lightenergycantravelthroughspace(avacuum)butsoundenergycannot.

Lighttravelsnearlyamilliontimesfasterthansound.Lighttravelsat300millionmetrespersecond

(or300000km/s)inairandsoundtravelsatabout330metrespersecond.

Bothlightwavesandsoundwavescanbereflected.Wehearareflectedsoundwaveasanecho.

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