How Does a Guitar Work?


Most human beings have heard a guitar played, either in person or through a recording. Few people, however, ever stop to wonder how a guitar works. Although the explanation can be complex, involving the physics of sound, the basic way in which a guitar works can be summarized more easily.

Sound is generated from a guitar when the strings are put into motion. Whether this motion is through strumming, plucking, or other means of making the strings move will affect the exact sound generated, but anything that vibrates the strings will produce a sound. The vibrations from the string produce a sound wave at a given frequency, determined by things such as the density of the strings and the tension with which they are stretched. The factors involved with this frequency of the sound wave being generated can also be explained in a much more elaborate fashion, but the basic idea here is that the movement and subsequent vibration of the guitar strings creates sound.

While causing some or all of the strings on a guitar to vibrate unhindered will produce a sort of chord, and while plucking the strings individually will produce separate notes, it is necessary for a guitar player to restrict the strings by some method to access a larger array of chords and notes. This is done by putting pressure on the strings in various combinations for a chord, or putting pressure on a single string for an individual note. Typically, a guitar player simply uses their fingers to create pressure on the strings, but any object that changes the tension of the strings will affect the tones produced by the guitar. When a guitar player becomes familiar with many chords, they are able to make their guitar play a wide spectrum of tones.

The strings create only a small amount of sound on their own, but aspects of the construction of a guitar serve to amplify the sound. The way in which sound from a guitar is amplified depends on whether the guitar is acoustic or electric.

In the case of an acoustic guitar, the sound waves produced by the vibrations of the strings are amplified by the body of the guitar. This is due in part to the hollow body of an acoustic guitar, but also because of the way in which the body is constructed. Guitar strings are attached to the body of an acoustic guitar at the bridge, which is located on the front of a guitar, near the open hole in the middle of the body. The front, or top plate, of an acoustic guitar is made of very light wood, and is designed to vibrate significantly. Braces on the back side of this piece keep the front relatively flat, but still allow the bridge to move freely. The vibrations of the strings cause the bridge to move, thus causing vibration in the top plate. These vibrations of the top plate are distributed over a much larger surface area than that of the strings, so the sound produced is increased in volume. For additional amplification of the sound, the sound waves bounce to the back of the guitar body, and then bounce towards the front of the guitar body, where they are released through the sound hole, which is designed to provide maximum amplification of the sound waves. So the combination of the strings, the bridge, the front and back of the guitar, and the sound hole allow an acoustic guitar to produce a louder volume of sound than strings attached to a plain board would produce.

Although in reality, an electric guitar is considerably more complex than strings attached to a plain board, electric guitars lack most of the amplification qualities of an acoustic guitar. Simply strumming or plucking the strings of an electric guitar will produce very little sound, unless the guitar is attached to an amplification device. Electric guitars create their sound electronically, through the use of magnetic pickups. The magnetic pickups register when the strings are vibrating, and transmit this information through a cord, connected to the electric guitar on one end and an amplifier on the other end. The amplifier then translates the information from the pickups, and produces a significantly louder sound than that of an acoustic guitar. That sound is then transmitted through a speaker on the amplifier. Furthermore, the sound waves from an amplifier speaker can be used to cause additional vibration of the guitar strings, creating a feedback loop. As the sound waves continuously vibrate the guitar strings, the sound can continue on indefinitely or until something is done to stop the strings from vibrating in this fashion.

The science of how a guitar works is obviously far more complex than this explanation. The basic physical actions of the parts of a guitar, however, can be simplified enough for the non-scientist to understand. Vibration causes sound waves, which are amplified either through construction or electronics, which allow us to hear and enjoy the music of guitars.