DAY 20 2017-02-07 Tue
本文基础:Ted-ed视频
最终誊写版：
434 words, 1 hour
How does a pluck on the guitar string make a melody at last? The scientific basics behind this conjure is sound waves.
This physic process starts from the vibration the string makes when plucked. The vibration is called a "standing wave". The fixed points ("node") and the rest of the oscillating points ("anti-nodes") on a string produce this vibration, which is then transported through the guitar neck and bridge to its body, a thin flexible wood. This standing wave keeps jostling the surrounding air molecules together and apart, together and apart, resulting in a sequential compression, i.e. sound waves, which the ears translate into electric impulses before human brain ultimately perceive as sound.
How is a pitch controlled so that a guitarist plays in tune?
A sound pitch is determined by the frequency of the compression: the more quickly the string vibrates, the more frequent the compressions, the higher the pitch. (Quicker vibrations produces higher pitch with more frequent compressions) And in order to know how the frequency of your string stands at, you need to know its length, tension, density and thickness, the latter two being the ultimate determinants which vary from guitar to guitar. In principle, thicker string will produce lower pitch because it vibrates more slowly.
To render a melody, getting the pitch right is not enough. While the pitch makes the final product of sound waves in tune, it is the overtone that gives a note its richness, making possible the melodious final product. One pluck at the string actually produces several waves, one fundamental wave and many overtones, the latter with a greater frequency. And where you pluck the string affects what overtones you get: odd multiple-overtones in the middle and even multiple-overtones near the bridge with a twangier sound.
In fact, this overtone series is the basis of western scale, which fills an octave (2 notes, one being twice the frequency of the other) with 12 half steps, each 2^1/12 more frequent than the previous one——exactly how the fret spacing on the guitar body is arranged: each fret being 2^1/12 more frequent than the previous one. Therefore, fretless instrument such as violin is difficult to control the pitch but more flexible to produce an infinite array of overtones (with different frequency).
New wave patterns can be created when two or more strings are played at the same time to produce chords or beats and more sound effects such as distortion, “wah-wah”, delay, flanger can be formed through the electrical processing between a pick-up and a speaker.
These are within human being’s ability. But imagine this. What if we have an infinite series of very tiny yet harmonic strings all mysteriously perfectly “manipulated” by an invisible hand of a higher being? Is that how everything is created in the universe?
初稿：341 words, 30 minutes
How does a pluck on the guitar string make a melody at last? It's all about sound waves.
This physics process starts from the vibration the string makes when you pluck a string. This vibration is called a "standing wave". The fixed points ("node") and the rest of the oscillating points ("anti-nodes") on a string produce this vibration, which is then transported through the guitar neck and bridge to its body, a thin flexible wood. This standing wave keeps jostling the surrounding air molecules together and apart, together and apart, resulting in a sequential compression, i.e. sound waves, which the ears translate into electric impulses before human brain ultimately perceive as sound.
How is a pitch controlled so that a guitar produces organised melodious sound instead of a jumble of unpleasant noise?
A sound pitch is determined by the frequency of the compression: the more quickly the string vibrates, the more frequent the compressions, the higher the pitch. (Quicker vibrations produces higher pitch with more frequent compressions) And in order to know how the frequency of your string stands at, you need to know its length, tension, density and thickness, the latter two being the ultimate determinants which vary from guitar to guitar. In principle, thicker string will produce lower pitch because it vibrates more slowly.
While the pitch makes the final product of sound waves intune, it is the overtone that gives a note its richness. One pluck at the string actually produces several waves, one fundamental wave and many overtones, the latter with a greater frequency. And where you pluck the string affects how the overtones render: odd multiple overtones in the middle and even multiple overtones near the bridge which produces a twangier sound.
In fact, this overtone series is the basis for western scale, which fills an octave (2 notes, one being the exact 2 times of the other in frequency)
But the pitch is not the only thing that ensures the product of a melody, which is formed through different notes in a scale. A scale is