Stem Instruments 20682b

The Recorder The recorder makes sound by splitting the air that is blown into it on a sharp edge. This air causes the pipe to vibrate. The air that goes through the instrument exits through the first open hole. This creates a note with a wavelength four times the distance from the hole to the air splitter. It is ¼ the wavelength because the air goes from high pressure at the splitter to the ambient pressure when it exits the instrument, creating ¼ of a wave. For example, the wavelength of a C4 is 132cm, so the recorder is 33cm long. The next sections of the wave go from ambient pressure to low pressure, then back to the ambient pressure, and finally back to the high pressure it started at. It does not have any extra amplification, but this could be achieved by adding a bell to the end like a clarinet. The bell increases the surface area of the vibrating pipe, causing it to move around more air, intensifying the wave and amplifying the sound.

The Ukulele The ukulele produces sound by changing the length of the strings and tightening the strings of the ukulele. The vibrations of the strings create the sound. The ukulele has finer strings causing it to vibrate faster and have higher notes. My strings are made of fishing line making them smaller than average guitar strings. Its wood frame helps amplify the sound it creates, if you were to put it onto a table it would increase its sound even more. Natural frequency is a sound an object makes naturally. The fishing line normally will not have a natural frequency because it is to limp. This ukulele can play the 5th octave.

Glass Harmonica The glass harmonica is made from a series of glasses secured to a base and filled with varied quantities of water to make each note. When you wet your finger and rub it around the rim of the glass it makes a high pitched hum. This is caused by the glass vibrating very quickly back and forth, not the water. The glass is elastic which means it will try to revert itself back to its original position. When the grooves of you finger catch on the glass it causes it to vibrate which in turn causes sound. The different glasses have different natural frequencies all depending on thickness, size, shape, and more. The water in the glasses weigh it down and partially prevent the glass from vibrating, changing the note. Picture of Instrument NOTE

WAVELENGTH (cm)

STRING LENGTH

FLUTE LENGTH

C4

132

66

33

D4

117

58

29

E4

105

52

26

F4

99

50

25

G4

88

44

22

A4

78

39

20

B4

70

35

18

C5

66

33

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The violin The violin produces sound when you drag your bow across the strings, and the strings vibrate. When the string vibrate it create a note, and each note have a certain frequency, the higher the frequency the higher the note. The violin has 4 strings each string plays a different note (G3, D4, A4, E5) because each string is tightened to a certain degree and each string has a different thickness and each note produces a different frequency (G3=196 Hz, D4=293.7 Hz, A4=440 Hz, and E5= 659.3 Hz). The nut and the bridge have to push on the strings at one relatively sharp point to prevent any unclean sounds.

The Math Every note has a unique frequency. In one octave, there are 12 notes, with the final note having twice the frequency of the first note. Using the note A4 (440Hz) as a reference, the frequency of a note n half-steps away from A4 is: 440Hz * ( √ 2 )n For example, C4 is 9 half-steps below A4, so its frequency is equal to 440 Hz * ( √ 2 )-9, or about 262 Hz. 12

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