A stringed instrument uses standing Strings: Guitar,...

Strings: Guitar, Harp, Piano and Harpsichord

Strings: Guitar, Harp, Piano Strings: Guitar, Harp, Piano and Harpsichordand Harpsichord

Physics 1251Physics 1251 Unit 2 Session 22Unit 2 Session 22Strings: Guitar, Harp, Piano & HarpsichordStrings: Guitar, Harp, Piano & Harpsichord

80/2080/20A stringed instrument uses standing A stringed instrument uses standing waves on a string to provide the waves on a string to provide the frequency generation.frequency generation.

♩♩ ♪♪ ♫♫ ff1 1 ff2 2 ff3 3 ff44fn

~~ ~~String Standing WavesString Standing Waves


A Standing Wave results from interference of A Standing Wave results from interference of countercounter--reflecting waves. reflecting waves.

L = L = 22//₄₄λλ11

λλ1 1 /4/4 λλ1 1 /4/4

Fundamental ModeFundamental Mode ff11 == vvstringstring / / λλ1 1 == vvstringstring / 2L / 2L

NodeNode NodeNode

AntinodeAntinode


80/2080/20The distance between neighboring nodes & The distance between neighboring nodes & antinodes is antinodes is ¼¼ λλ. [ . [ ““NN--A d = A d = ¼¼ λλ”” ]]

NodeNode NodeNode NodeNode

AntinodeAntinode AntinodeAntinode

λλ2 2 /4/4 λλ2 2 /4/4 λλ2 2 /4/4 λλ2 2 /4/4

L = L = 44//₄₄λλ22

Second HarmonicSecond Harmonic ff22 == vvstringstring / / λλ2 2 == vvstringstring / L / L


The Vibrating String DemonstrationThe Vibrating String Demonstration

Physics 1251Physics 1251 Unit 2 Session 21Unit 2 Session 21Scales and StringsScales and Strings

80/2080/20Frequency of nFrequency of nthth harmonic:harmonic:

ffnn = [2n/(4L)] = [2n/(4L)] ‧‧ vvstringstring

ffnn = [n/(2L)] = [n/(2L)] ‧‧ √√(T/ (T/ μμ)])]


80/2080/20The modes that will be present are The modes that will be present are those that are excited.those that are excited.

♩♩ ♪♪ ♫♫ ff1 1 ff2 2 ff3 3 ff44fn

~~ ~~Energy source can excite Energy source can excite

selected modesselected modes


80/2080/20The modes that will be present are The modes that will be present are those that are excited.those that are excited.

Example: Guitar Overtones (Harmonics)Example: Guitar Overtones (Harmonics)Plucking, strumming, dampingPlucking, strumming, damping


The The GuitarGuitar is a fretted stringed instrumentis a fretted stringed instrumentthat is plucked or strummed.that is plucked or strummed.

NeckNeck

BodyBodyStrings (6) Strings (6)

Tuning pegsTuning pegs

BridgeBridge

FretsFrets


Density of strings sets range of each stringDensity of strings sets range of each string

Denser wire: lower pitchDenser wire: lower pitch

Less dense wire: Less dense wire: higher pitchhigher pitch


Frets shorten the string to raise the pitch.Frets shorten the string to raise the pitch.LLoo

LL11

Fret Fret LLo o // LLnn11 1.061.0622 1.121.1233 1.201.2044 1.271.2755 1.331.33


The tuning pegs change the string tension.The tuning pegs change the string tension.

Tuning PegsTuning Pegs


The strings are attached to the body and The strings are attached to the body and sound board by a flat sound board by a flat bridgebridge..

BridgeBridge

StringsStrings


80/2080/20The coupling of the string to the sound The coupling of the string to the sound board will accentuate or attenuate board will accentuate or attenuate various frequencies.various frequencies.

♩♩ ♪♪ ♫♫ ff1 1 ff2 2 ff3 3 ff44fn

~~ ~~Sound Board and Acoustics filter Sound Board and Acoustics filter

harmonicsharmonics


The response of the body and air cavityThe response of the body and air cavitydetermine the filtering of the harmonics.determine the filtering of the harmonics.

BridgeBridgeSound holeSound hole

Truss rodTruss rod

BodyBody

NeckNeckGuitarGuitarin cross sectionin cross section


Vibration Modes of Guitar Body:Vibration Modes of Guitar Body:Holographic vibration images Holographic vibration images

of Guitar bodyof Guitar body


80/2080/20A A HarpHarp is a stringed instrument that is is a stringed instrument that is plucked. Its strings are of various plucked. Its strings are of various lengths.lengths.

Traditional Traditional Irish HarpIrish Harp

StringsStrings

Sound BoardSound Board


The principal pitch of each string in a The principal pitch of each string in a Pedal HarpPedal Harpis determined by its length. is determined by its length.

Pedal HarpPedal Harp

However, depressing a pedal shortens or lengthens the string However, depressing a pedal shortens or lengthens the string length, raising (or lowering) the pitch incrementallylength, raising (or lowering) the pitch incrementally..

StringsStrings

PedalsPedals


The principal pitch of each string in a The principal pitch of each string in a Pedal HarpPedal Harpis determined by its length. is determined by its length.

However, depressing a pedal shortens or lengthens the string However, depressing a pedal shortens or lengthens the string length, raising (or lowering) the pitch incrementallylength, raising (or lowering) the pitch incrementally..


80/2080/20A Harpsichord is a keyboard stringed A Harpsichord is a keyboard stringed instrument whose strings are plucked. instrument whose strings are plucked. Each string is used for one pitch only. Each string is used for one pitch only.






80/2080/20A Harpsichord is a keyboard stringed instrument A Harpsichord is a keyboard stringed instrument whose strings are plucked. whose strings are plucked. Each string is used for one pitch only. Each string is used for one pitch only.

KeyKey

JackJackStringStringPlectrumPlectrum

DamperDamperHarpsichord Harpsichord ActionAction


80/2080/20A Harpsichord is a keyboard stringed instrument A Harpsichord is a keyboard stringed instrument whose strings are plucked. whose strings are plucked. Each string is used for one pitch only. Each string is used for one pitch only.


The jack plucks in one direction, The jack plucks in one direction, then retracts in the opposite.then retracts in the opposite.


80/2080/20A A PianoPiano is a keyboard stringed instrument is a keyboard stringed instrument whose strings are hammered. Each string is whose strings are hammered. Each string is used for one pitch only. used for one pitch only.

StringsStrings

Key BoardKey Board

Sound Sound BoardBoard

FortepianoFortepiano PianoPiano


The Piano strings are hammered by a felt The Piano strings are hammered by a felt hammer, actuated by the hammer, actuated by the ““action.action.””

JackJack KeyKeyHammerHammer

String and DamperString and Damper


The Piano strings are hammered by a felt The Piano strings are hammered by a felt hammer, actuated by the hammer, actuated by the ““action.action.””


80/2080/20A A PianoPiano has multiple strings (in the treble) to has multiple strings (in the treble) to provide a more powerful sound.provide a more powerful sound.

Multiple StringsMultiple Strings

Sound BoardSound Board BridgeBridge FrameFrame


Piano strings are tensioned by tuning pins in a Piano strings are tensioned by tuning pins in a strong frame.strong frame.

FrameFrame

Tuning PinsTuning Pins

Bass StringsBass Strings


Piano hammers are made of felt and wood.Piano hammers are made of felt and wood.

Pivot hingePivot hinge

Hammer HeadHammer Head

Back CheckBack CheckFeltFelt WoodWood


The timbre of the piano sound is affected by the The timbre of the piano sound is affected by the hardness of the hammer felt.hardness of the hammer felt.

Felt Felt ––

hard or soft?hard or soft?

A stringed instrument uses standing Strings: Guitar,...

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