Amazing Kids! Magazine

SciTech Kids! – The Mechanics of an Electric Guitar & Amplifier

By: Patrick Bradshaw, Contributing Writer

Have you ever been to a rock concert or watched someone play electric guitar? Have you ever wondered how the guitar works, how the sound goes from the string to your ears? This process involves several stages and parts. However to understand the basis of it, we must first discuss how you hear a sound.

When you hear a sound, your ear interprets waves of compressed, high-pressure air as different noises and different pitches. These waves of air, or sound waves, are created by vibrations in whatever object is making the noise, like your vocal chords when you speak. When you talk, the air rushes past your vocal chords and they vibrate, creating different sounds. So if you were to put your hand on your neck while talking, you could feel your entire throat vibrating. Try it out! The same principle applies to both the guitar and the amplifier (amp), because when you strum the strings and they vibrate, they create a sound. In the amp, the speaker vibrates, creating the sound that you hear. However, we’ll get into that idea later.

Before any electronic “stuff” happens in the guitar, the strings have to be strummed or plucked to make a sound, just like we said earlier. Well, how come each string makes a different sound? Each of the six strings on a standard guitar has a different weight, or thickness, which causes them to vibrate at different speeds. The thicker strings vibrate more slowly, and thus make a deeper sound. The same concept is applied when tuning the guitar. To tune each string, the guitarist uses the knobs on the head stock of the guitar to tighten and loosen the string. The tighter the guitarist makes the string, the higher the pitch of the sound the guitar makes. Similarly, by placing your fingers on a flat part of the neck and pushing down firmly on a string, the string will make a higher pitch noise because the area over which it vibrates has been lessened and the string has been tightened by your finger. The purpose of the frets, other than to mark the location of the most commonly used sounds (keys in musical terms), is to smoothen out the sound by providing a smooth and firm base to stop the string’s vibrations. Fretless guitars and bass guitars do exist and they do work, making smooth sounds, however they are more difficult to play and the frets help the guitarist change the sounds that they make more quickly, smoothening out the rough position of their fingers.

Ok, so now we have a sound coming from the strings, but how does that get from the string to the amp? Before we dive into this, let’s split it up into a two-part process. First the sound has to get from the strings to the pickups on the guitar, and then it has to get from the pickups to the amplifier. So what exactly is a pickup? A pickup is a machine on the guitar that converts a select range of mechanical sound waves into electrical signals, or in other words, an electronic ear converts the sound made by the strings into a format that is readable by the amplifier. However, depending on where the pickup is on the guitar, the sound is interpreted differently because the string doesn’t vibrate uniformly the entire way through. Once the pickup has converted the sound wave into an electrical signal, it sends the signal out through a chord and into an amplifier. On its way, either in the amplifier or in foot pedals, the signal can be modified using preset effects, changing the end sound slightly. These effects that are applied to the signal are purely electrical and change only the signal, not the initial sound of the string. Some examples of these effects are: distortion – which gives the guitar a grungier sound, phaser – which gives the sound a more synthetic feel while it switches between a slightly higher and slightly lower pitch, and echo – which, like it sounds, echoes the sound of the guitar.

Finally, once the signal has reached the amplifier and all desired effects have been applied to it, the electronics inside of the amplifier read this signal and convert it into vibrations. It vibrates the speaker at precisely the right frequencies to create the desired sound. This is why old speakers can go “flat,” because as they get older, they are unable to vibrate as effectively, and will often vibrate slower than the signal tells them to, giving the sound a lower pitch. However, the vibrations of the speaker in the amplifier have much more power behind them, which causes the sound to be louder. They amplify the sound, hence the name amplifier.

In summary, the path of sound in an electric guitar involves many stages and steps. From strumming the string, to converting the sound to an electrical signal, all the way to converting that signal back into sound waves, the initial sound undergoes many changes and demonstrates the necessity of every piece of the guitarist’s equipment. So there you have it, the mechanics of an electric guitar. Rock on!

One comment

  1. this was great learning about all those cool things of guitars!