how musical instruments work

8/10/2019 How Musical Instruments Work

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Nakul Abhyankar 08M129


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Guitars are the most popular and commoninstrument of the string family. The guitarhas been around for thousands of years andis still prominent in modern music. While aguitar is not the most complicated instrumentthere still is a lot of physics behind theprocess of making sound from a string. Tofully understand how a guitar works we firstneed to understand what exactly sound is, sothats where well start.


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Sound is energy in the form of waves caused by vibrationFormed when air particles vibrate from the vibrating objectaround them and travel in wave shapes called longitudinalwaves.The waves are made up of areas of high pressure calledcompressions and areas of low pressure calledrarefactions


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WAVE LENGTHThe wave length of a sound wave is one complete cycle of the wave attwo equal successive points. (one compression and rarefaction)

AMPLITUDEThe amplitude is the height of the wave. The higher the amplitude thelouder the wave.


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FREQUENCYThe frequency of a sound wave is the number of cycles that

pass a certain point in a second. Frequency is measured inHertz. Another way of talking about frequency is pitch. Theyare basically the same thing. The higher a sounds pitch is thehigher the frequency of the wave. Pitch is usually associatedwith music.

VIDEO OF DIFFERENT FREQUENCIEShttp://www.youtube.com/watch?v=igGroIcga3g&feature=related
http://www.youtube.com/watch?v=igGroIcga3g&feature=relatedhttp://www.youtube.com/watch?v=igGroIcga3g&feature=related


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The most important part to a guitar sound is the stringsModern guitar strings are usually made from either nylon or steel, nickel, andbronze.They are stretched from the bridge of the guitar over the body and fretboard, against the nut and into the tuners (which adjusts the tension of thestrings to the desired notes).

When the guitar player plucks the strings it causes them to vibrate whichcauses the air around the string to vibrate thus making a sound wave.The frequency that a string produces is determined by the mass, length, andtension of the string.

Heavier strings vibrate more slowly Higher tension raises the pitch Shorting the string raises the pitch


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Strings are fixed at each end which is why they are able to vibrate.The parts of the string that are unable to vibrate are called thenodes. The parts where vibration is present are called antinodes.When the string is plucked the note we hear is called thefundamental frequency or the 1 st harmonic. There are also manyother frequencies that are produced when the string is plucked.These other frequencies are called Harmonics or Overtones.


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When a string is plucked it vibrates in more than one way. The string vibratesin many different shapes and directions which produce many differentamplitudes and frequency waves which are called harmonics.The string can vibrate as if it was two half strings with a node in the middleor as three third-strings and so on.The harmonics are not regular sound waves they are called standing waves

because they do not travel.Harmonics are what causes a guitar to sound the way it does and not justboring simple sounds.

Good Animation:http://id.mind.net/~zona/mstm/physics/waves/standingWaves/standingWaves1/StandingWaves1.html
http://id.mind.net/~zona/mstm/physics/waves/standingWaves/standingWaves1/StandingWaves1.htmlhttp://id.mind.net/~zona/mstm/physics/waves/standingWaves/standingWaves1/StandingWaves1.html


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BODY


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If it wasnt for the body of a guitar the vibration of the strings would barely beaudible. The body of the guitar amplifies the sound of the strings so thesound can be heard.

When the player plucks the guitars strings, the strings vibrate, which transfersthe mechanical energy down the strings to the guitars bridge which isattached to the guitars body. When the energy is transferred to the bridge it

cause the top plate (also called the soundboard) of the body to vibrate aswell. The sound board is usually made form a thin piece of wood withbracing on the underside to support the soundboard but this bracing alsohas a significant impact on the sound the guitar makes.

BRIDGE


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When the soundboard of the guitar vibrates itcauses the air inside the body of the guitar tovibrate as well.When the molecules of air closest to the

soundboard start vibrating they bump into theother particles around them and they start tovibrate and so on.The air particles inside the body are vibrating at a

common frequency which is the sound that isproduced. All the air inside the body of the guitar is vibratingand this sound and vibrating air has to gosomewhere.


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The sound hole iswhere all thevibrating air andsound escapes fromthe guitars body.Which is how thesound of the

instrument isprojected to thelisteners.


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The s xophone (also referred to as the s x ) is a musicalinstrument that is a conical bored- transposing ofthe woodwind family. Saxophones are usually made of brass andplayed with a single- reed mouth piece similar to that of

the clarinet.


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The saxophone player provides a flow of air at a pressure abovethat of the atmosphere.This is the source of power input to the instrument, but it is asource of continuous rather than vibratory power.In the saxophone, the reed acts like an oscillating valve(technically, a control oscillator). The reed, in cooperation withthe resonances in the air in the instrument, produces anoscillating component of both flow and pressure.Once the air in the saxophone is vibrating, some of the energy isradiated as sound out of the bell and any open holes.


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A ree is a thin strip of material which vibrates to produce asound on a musical instrument.A player blows air into the saxophone through the reed.


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When air is blown into the reed, there is a pressure difference created.When this pressure difference increases, more air should flow through the

narrow gap left between the tip of the reed and the tip of the mouthpiece. So agraph of flow vs pressure difference starts off almost proportionally.

as the pressure gets large enough to bend the reed, it acts on the thin end ofThe reed and tends to push it upwards so as to close the aperture throughwhich the air is entering.


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Saxophone is a closed type pipe. It is conical in shape but thereare saxophones who have a U bell to give some specialtimbres.he saxophone doesn't come to a sharp point: it has amouthpiece.Since it is a closed pipe, antinode is formed at the reed and theother node is formed at an open hole.saxophone is approximately conical. This means that soundwaves 'spread out' as they travel down the bell. This means thatthe amplitude of the waves gets smaller as we go frommouthpiece to bell.


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This is how a standing wave is formed for different notes.This shows that as we open the holes from bottom to top, the

standing wave becomes shorter and higher notes are played. Starting near the bell, each opened tone hole raises the pitch by a

semitone, which requires a pipe that is about 6% shorter.

The bell 'helps' the sound waves in the bore to radiate out into the air.More sound radiated means less sound reflected, so the standing

waves are weaker. However, this effect is only strong for highfrequency: as the frequency increases over this range, the resonancesare more weakened by the bell at high frequency than at low. This isbecause the bell is much smaller than the wavelengths of the low

frequency waves, and so is less effective at radiating these waves.
http://www.phys.unsw.edu.au/jw/strings.htmlhttp://www.phys.unsw.edu.au/jw/strings.htmlhttp://www.phys.unsw.edu.au/jw/strings.htmlhttp://www.phys.unsw.edu.au/jw/strings.html


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how musical instruments work

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