Note:
pluck a string—standing wave(驻波)—nodes(still)/anti-nodes(oscillate)—the vibration translates through the neck and bridge to the guitar’s body—wood vibrates—air molecules jostled – creating sound
Pitch: decided by frequency—frequency decided by four factors: length, tension, density and thickness – the thicker, the slower, the lower
Several standing waves:
the first fundamental wave decides the pitch
overtones: changed by the way you pluck the string—in the middle:fundamental waves and odd overtones/near the bridge: even multiple overtones
We can hear the world because our brain translates vibrations in the air into electric signals which we recognize as sounds. The same rule applies to the sound of the guitar. When you pluck a string, you actually create a series of standing waves, with nodes, those points that stand still and anti-nodes, those that oscillate back and forth. The vibration then translates through the neck and bridge to the guitar’s body and reaches the thin and flexible wood. Most of it escapes from the hole in the wood and reaches our ear, thus creating sound.
We hear notes of different pitches because the vibrations bear various frequencies. Frequency is decided by four factors, length, tension, density and thickness. While the strings are the same in length and tension, density and thickness varies to create different pitches. The thicker the string, the slower the vibration, thus producing a note with a lower pitch.
The fret space of the guitar is decided by frequency of each note. The western scale is based on the overtone theories of a vibrating string. When one note has the frequency exactly twice of another, they sound similar to us and we call the difference between them an octave, and squeeze the rest of the notes in between. Each of the twelve half steps has the frequency 2^12 higher than its previous one, which determines the fret space of the guitar.
Though the major parts of the guitar remain the same, shape and material can be changed to produce sounds with a unique quality.