The Physics of a Guitar
What are the physical principles behind our guitar playing?
Firstly, how does a guitar make sounds and then perceived by our ears? Actually, when you pluck a guitar string, you create vibrations called the standing waves. The vibration translates through the neck and bridge to the guitar’s body where the thin and flexible wood vibrates，hustling the surrounding air molecules together and apart. These sequential compressions create sound waves and the ones inside the guitar mostly escape from the guitar’s hole. They eventually propagate into your ears which translate them into electrical impulses that your brain interpreted as sounds.
Then, how does a guitar player make different sounds that vary in pitch and rhythm, thus constituting a piece of music? Well, there The pitch of the sound depends on the frequency of the compressions. A quick vibration will cause a lot of compressions close together, making a high pitch sound. And a slow vibration creates a low pitch sound. Four things affect the frequency of a vibrating string--the length, the tension, the dense and the thickness. Typical guitar strings have similar length and tension, but vary in dense and thickness--thicker strings vibrate more slowly, producing lower nodes. Each time you pluck the string, you actually create several standing waves, and among them there are the first fundamental waves and the overtones-- the first determines the pitch of the node while the latter’s frequencies are multiples of the first and change according to the way you pluck the strings. Different octaves made from different frets on the guitar also contribute to different sounds. When you play two nodes which frequencies are close together, they add together to create a sound wave whose amplitude rises and falls. The guitar players call this effect the beats.
What’s more, the electrical guitar provides various ways to process the wave between the pickups and the speakers, thus making effects like distortion, overdrive, Wawa, delay and flanging.
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