Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: i am bored on 26/04/2007 01:35:37
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I play the saxophone in my school band. I already knew that the reed made the sound but i want to know what makes the saxophone vary in pitch.
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It's to do with making the air vibrate. Lower notes on the sax are achieved using buttons lower down. Therefore there is more air between the reed and the first hole where the air can escape. That means you set up a longer wavelength in the air. Longer wavelength = lower pitch.
It's the same principle as the strings on a violin or guitar. The higher up the neck you press the string, the shorter the part of the string you bow or pluck & the higher the pitch of the note.
What puzzles me, though, are trumpets. How do you get so many notes with only 3 holes? [???]
Afterthought - my girlfriend gets a lot of notes from my wallet and she's only got 3... NO, I CAN'T SAY IT!
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What puzzles me, though, are trumpets. How do you get so many notes with only 3 holes? [???]
Afterthought - my girlfriend gets a lot of notes from my wallet and she's only got 3... NO, I CAN'T SAY IT!
the word you are looking for is "fingers". how does she get all the money from your wallet when she only has three fingers
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The reed opens and shuts sharply making the air flow start and stop very abruptly
[diagram=209_0]
In order to make this air flow up from sine waves you need a huge number of different ones. So you are putting lots of different pitches into the body of the instrument.
The instrument will then resonate at some frequencies better that other. Think of it like a swing - if you are sitting on a swing and wobbling your legs, if you do it at the right speed your swing builds up and your input is amplified, but do it at any other speed and you don't swing at all.
Air rushing up and down the body of the saxaphone will tend to resonate at certain frequencies (pitches) these will mostly depend on how long the pipe is - a longer pipe takes more time for the air to rush up and down it, so is at a lower frequency. Opening holes will alter the length that the pipe behaves as if it is, so altering the pitch.
A trumpet works on a similar principle, but because you only have 3 buttons and therefore 6 lengths of tube you have to take advantage of something called harmonics.
A tube or a stretched string actually has several frequecies it will resonate at. I will draw a string as it is easier:
[diagram=210_0]
A trumpet can make so many notes becasue the trumpet player can alter the properties of his lips to change the frequencies going into the body of the trumpet. This means he can pick which of the harmonics are going to get amplified. So increasing the number of notes he can play.
I think you can do something similar, but less sophisticated by overblowing a reed instrument. This increases the speed of the reed so much it isn't feeding any of the low frequencies in so you just hear the higher harmonics.
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Indeed you can "overblow" the reed by squeezing tighter with your lips (tightening one's embrochure).
Guitars can be made to emphasise harmonics in a couple of ways. When using a plectrum, pick the string at 1 of the harmonic points and brush the side of your thumb on the string as you do so. This is the technique rock guitarists use to get the high screaming sound from their instruments.
Classical guitarists, on the other hand, use a different technique. This involves lightly pressing the tip of a finger on the string at the harmonic point while plucking the string and lifting the finger as you pluck. Most commonly this is done pressing the tip of the index finger on the string while plucking with the 3rd finger.
Another technique is to use your thumb and finger to pluck either side of the same string at different points at the same time.
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It's to do with making the air vibrate. Lower notes on the sax are achieved using buttons lower down. Therefore there is more air between the reed and the first hole where the air can escape. That means you set up a longer wavelength in the air. Longer wavelength = lower pitch.
It's the same principle as the strings on a violin or guitar. The higher up the neck you press the string, the shorter the part of the string you bow or pluck & the higher the pitch of the note.
What puzzles me, though, are trumpets. How do you get so many notes with only 3 holes? [???]
Afterthought - my girlfriend gets a lot of notes from my wallet and she's only got 3... NO, I CAN'T SAY IT!
When playing the trumpet (or any brass) you have to make a buzzing action into the mouth piece to make a noise. The pitch of the note determines how tight you blow/buzz into the mouth piece. My old teacher could play a song with out his trumpet just by buzzzing the notes.