Electric guitars are one of the most popular instruments in the world, but what many people don’t know is that electric guitars are fairly complicated on a physics level. While other instruments use the air alone to conduct soundwaves, electric guitars conduct sound in a different way.
Electric guitars work by using magnetic conductors called Faraday coils to pass electrical impulses. These impulses are converted into audible sound through an amplifier. Amplifiers then transmit those impulses from the guitar into a loudspeaker to create music.
An electric guitar might seem complicated because of all the bells and whistles they usually include, but the physics behind how they work is surprisingly simple. Keep reading to learn all about how electric guitars work.
What Powers an Electric Guitar?
Like it says on the label, an electric guitar is powered by electricity. However, it’s a little bit more complicated than just that. An electric guitar also transforms the vibrations created by the strings into electromagnetic energy. This process works on two major principles:
- Electromagnetic induction: In electromagnetic induction (also known as Faraday’s law of induction), a conductor is capable of producing an electromotive force within a fluctuating magnetic field. In electric guitars, adjusting the magnetic fields around magnetic pickups is what changes the pitch and tone of the guitar’s sound.
- Electronic amplification: In electric guitars, amplifiers take the vibrations produced by the electric guitar and make them louder. Electrical amplification increases the amount of energy in the sound wave, which in turn increases its volume. Electric amplifiers add energy to increase volume by uptaking energy from an outside electrical source.
The combination of these two physics properties—induction and amplification—creates the sound of the electric guitar. Without the physical force of electromagnetism, an electric guitar wouldn’t work at all.
Parts of an Electric Guitar
When it comes to electric guitars, the strings and the body are just the foundation of the instrument. Inside of the guitar, there are complex components that are used to both generate and transmit electromagnetic impulses into audible sound.
Here are the major parts of the electric guitar that create sound:
- Magnetic pickups: The magnetic pickups in electric guitars typically consist of magnets that have been tightly wrapped with copper wire. These transducers produce a fluctuating magnetic field that the guitar player manipulates by operating the strings.
- Amplifier: An amplifier is the part of the guitar that increases its volume by amplifying the guitar’s sound waves. This is done by funneling energy from an outside energy source and adding it to the sound, exciting the sound waves and increasing their amplitude.
- Metal strings: The metal strings are the part of the guitar that forms the primary input on the guitar. The pitch of the strings is determined by their diameter and tension. A metal string forms a standing wave because it is fixed at either end, which means that it can be made to vibrate and produce a particular pitch every time it is plucked.
- Electrical circuits: In the electrical circuits of a guitar pickup, the magnetic pickups along the fretboard form a circuit between the toning knobs, the pickup selector switch, and the output jack. The electrical circuit also connects to the amplifier via the output jack.
- Tuning knobs: The tuning knobs on an electric guitar are used to adjust the tone and volume of the guitar. The tuning knob controls a potentiometer that acts as an equalizer to filter out either higher or lower frequencies than the main pitch being played on the guitar. The higher the guitar is tuned, the more crisp and clear the sound is.
As you can see, the electric guitar has many different interworking parts. But the advantages of an electric guitar are that the pitch and tone of an electric guitar are easier to manipulate than the pitch and tone of many other instruments.
The Physics of an Electric Guitar’s Sound
When an electric guitar produces sound, it does so through the vibration of the strings. The pitch and tone of the sound are manipulated through the tension on the strings and the weight of the string. The larger the diameter of the guitar string, the slower it will vibrate when plucked. This creates a lower pitch.
In electric guitars, the pitch of the strings is adjusted by tweaking the tuning keys to adjust the tension on the strings. An electric guitar also has a tuning knob in addition to the string keys, but instead of adjusting the tension on the strings, these knobs adjust tone and volume.
Along with a tuning knob that adjusts tone and volume, an electric guitar has tuners that are used to adjust the pitch of individual strings.
What is the Difference Between Pitch and Tone in Electric Guitars?
Both the pitch and the tone on an electric guitar can be adjusted, but what is the difference between these two aspects of sound physics?
- Pitch: In electric guitars, the pitch of the guitar is the frequency of the vibration that the electric guitar’s string produces. Standard pitches that are used to compose music are known as musical notes.
- Tone: Tone is the result of multiple sound frequencies being played simultaneously. The word tone is often used interchangeably with the term timbre. In electric guitars, a tone can be created either by striking multiple strings at once or by adjusting the tone knob.
Together, pitch and tone combine with other sound effects such as distortion and reverberation to create the sounds of the electric guitar.
Sound Waves on an Electric Guitar String
Guitar strings work on a physical level by forming a standing wave. A standing wave (which is often called a stationary wave in physics) oscillates in time but has a peak amplitude that does not move in space. In physics, a sound wave can take on either a longitudinal or a transverse wave. But in fluid mediums like the air, sound waves can only travel longitudinally.
The speed of the string’s oscillation and the pitch of the resulting soundwave depends on two factors:
- String density: The string density on electric guitars is determined by their gauge. The lower the gauge of the guitar, the higher the tension in the string, and the higher the pitch on the string is. Heavier gauge or thicker strings can’t hold as much tension as thinner strings and will produce a lower pitch.
- String tension: The tension on a guitar string determines pitch along with the string’s density. The tension on most guitar strings ranges between 60 and 80 Newtons. String tension is one aspect of the guitar that is most easily manipulated by the electric guitarist while playing in order to change its sound.
The velocity of the moving guitar string is determined by combining the string’s velocity and wavelength. All six strings on an electric guitar operate on the same wavelength since they are all the same length on the body of the guitar. This means that the pitch on a guitar string is manipulated by changing the speed of the string’s vibration instead.
How Do Magnetic Pickups Work?
If you had to point out one component of the electric guitar that makes it stand out against other guitars in how it works from a physics standpoint, you could look at the magnetic pickups. The magnetic pickups generate magnetic fields that fluctuate depending on how the guitar strings are held and struck.
Through the magnetic pickups, the metal strings of the guitar itself become slightly magnetized. The magnetic pickups convert this magnetism to a small electrical current, which is fed into an amplifier to increase its volume.
How Many Magnetic Pickups Does an Electrical Guitar Have?
The number of magnetic pickups in an electric guitar varies depending on the type and complexity of the electric guitar. Many standard guitars have three pickups. Some have only one or two, and others have five. It depends on the model and guitar type.
The more magnetic pickups an electric guitar has, the more nuanced the guitar’s sound control is. Magnetic pickups are set at different points along the body of the guitar. Pickups can usually be located at the neck, middle, and bridge of the guitar. This allows magnetic pickups to provide more tonal control over the guitar’s pitch.
What Kind of Magnetic Pickups Are There?
Magnetic pickups come in two major types: single coil and humbucker (double coil). Functionally these coils operate the same way on a physics level. Whether a guitarist uses a guitar with a single coil or humbucker magnetic pickups is based solely on preference. However, these two pickup types do have slightly different sounds.
- Single coil: Single coil pickups are known for having a bright tone in comparison to humbucker magnetic pickups, which makes them popular with country and surf guitarists. With certain playing techniques, single coil pickups can also play a glassy or chiming tone compared to double coil pickups.
- Humbucker coil: A humbucker or double coil pickup was introduced to electric guitars to combat the buzzing distortion created by amplifiers and volume knobs. Compared to single coil pickups, a humbucker coil gives the guitar strings a thicker, richer sound. Some humbucker coils can be separated to create a sound more similar to a single coil.
Why Do Guitarists Still Use Single Coil Magnetic Pickups?
If many humbucker coils are able to emulate the sound of single coil magnetic pickups, then why are guitars still created with single coils? This is because single coils offer a distinctly different sound.
If you listen to the music of Jimi Hendrix and Carlos Santanas back to back, you’ll be able to notice that the guitars in their music have slightly different tones. This is because Jimi Hendrix was a single coil player, and Carlos Santanas is known for playing humbucker guitars. Casual music listeners may not be able to hear much of a difference, but to trained musicians, the differences are as clear as a bell.
Magnetic pickup type is also determined by the type of guitar. Fender guitars are known for their single coil sound, while Gibson guitars have humbucker pickups. The choice of magnetic pickups in these brands is mostly a matter of tradition. Both manufacturers also create hybrid pickups.
How Do Amplifiers Work?
Amplifiers are used as a middleman between the electric guitar’s electrical circuits and a loudspeaker used to amplify (or increase the volume of) the guitar’s sound. Amplifiers work by using the electric currents generated by the guitar’s strings during play and interpreting them into audible sounds. The amplifier boosts the electric current until it is strong enough to drive an electric speaker.
Amplifiers do more than just boost an electric current, however. Amplifiers also convert the signal generated by the electric guitar into an entirely new output signal by converting the electrical current in the guitar from alternating current to direct current. This smooths out the signal and makes sure it is uninterrupted for a clear sound.
Amplifiers operate by taking in the electrical signal from the guitar and passing it through an input circuit. This circuit applies varying resistances to the signal to reproduce the electrical current fluctuations produced originally by the guitar strings.
In many amplifiers, the work of boosting the sound signal falls to two separate components: the pre-amplifier and the power amplifier. The amplifiers use semiconductors known as transistors to boost the voltage of the incoming guitar signal.
Does an Electric Guitar Work Without Electricity?
If an electric guitar works on the physical concept of electromagnetic induction, can you play an electric guitar without electricity?
An electric guitar can’t be played without electricity because it isn’t built that way. Rather than having a hollow body to act as an amplifier for the natural vibrations created by the guitar strings, an electric guitar is filled with electrical circuits and Faraday coils.
Without electrical power, an electric guitar has no amplification at all. They’re just not designed for being used without a power source. That doesn’t mean that a guitarist can’t practice on an electric guitar without power. It just means that the sound of the guitar will be soft and tinny. It is loud enough for the musician to hear the notes, but not loud enough to perform.
Can You Plug Headphones into an Electric Guitar?
You can’t plug headphones in to hear the sound of an electric guitar with no power source. This is because, without electricity, there is no amplification. Headphones are just an output and still require an electric signal to convert the sound waves on the guitar strings in order to hear them.
Can Magnets Damage Electric Guitar Pickups?
While high-powered magnets can potentially damage electric guitar pickups, this is a relatively rare occurrence.
The main reason for this is that the magnetic field passed over an electrical pickup from a magnet is relatively slow, while the magnetic field generated by electrical pickups is oscillating at a rapid pace. The magnetic field of an interfering magnet will not produce enough electric current in comparison to the string to affect the sound of the guitar.
One thing to avoid with electric guitars is leaning them up directly against their amp facing forward. This places the magnetic pickups right next to the large speaker magnet contained in most amplifiers. In proximity to the stronger magnetic, this can cause the magnetic pickups in the guitar to be degaussed, or to lose their magnetism. Over time this can cause the neck pickups on the guitar to become weaker.
Another way that magnets can damage electric guitar pickups is if a regular soldering iron is used to solder pickups into the guitar. Instead, a specialized soldering iron with a separate power source must be used to keep the magnetized part of the iron away from the pickups. Good news, though—even if an electric guitar’s pickups are degaussed, they can be recharged again.
Harmonic Content and Electric Guitars
In sound physics, the harmonic content of a soundwave is an integer multiple of a fundamental musical tone. In simpler terms, harmonics are the result of multiple musical frequencies overlapping. In string instruments like guitars, a natural harmonic is a harmonic that is played on an open string. Artificial harmonics are created by fretting or fingering the guitar strings.
Harmonic content determines the timbre of the guitar. Timbre is what gives each sound made by the electric guitar its “color.” Timbre is defined by several descriptors and can range from warm and dark to bright and brassy. Timbre is one of the most subjective descriptors of a sound and encompasses all parts of the sound that don’t involve the following:
Even though harmonics feature mixed sound frequencies, the human ear does not interpret these vibrations as individual frequencies. Instead, they mesh together to form a deeper and richer note. The slight differences in harmonic balance are what chance the color and timbre of an electric guitar’s sound.
In a harmonic, the fundamental is the main note you hear- it vibrates at a lower pitch. In contrast, the harmonics are formed by additional higher frequencies known as overtones. It is the overtones that determine the timbre of the sound.
This is what allows listeners to be able to determine the difference between the sound in two different electric guitars. Even when playing the same note, the two guitars are likely to sound different based on their timbre.
String-Bending and Electric Guitar Physics
String-bending is a way of playing the electric guitar that further manipulates the sound frequencies produced by the instrument. By pressing a string down towards the fret of the guitar, the guitarist raises the pitch of the sound played from it. This action increases the vibrating length of the note while also increasing tension.
Fretting—or holding the strings down directly against the guitar’s fret—also changes the pitch and tone of the note being played. The distance between the fret of the guitar and the strings on the guitar is known as the guitar’s action.
Low-action guitars that don’t have a lot of space between the fret and the strings are easier to fret, but they can create a buzzing noise if the strings vibrate directly against the fret. High-action guitars are harder to fret but have a cleaner sound.
Vibrato in Electric Guitars
One technique that is often used to manipulate the soundwaves generated by an electric guitar is vibrato. This is when a guitar’s pitch is modulated at a regular rate to produce a warbling sound. Vibrato is one of the most common ways a musician adds expression to a musical note. In electric guitars, vibrato is created by wiggling a finger on the string to modify the tension being placed on it.
Vibrato in guitar-playing is defined in two ways:
- Fast/slow: The speed of vibrato in electric guitars refers to how quickly the guitar player uses their finger to displace tension on the string. This manually manipulates the pitch of the note in a controlled way.
- Wide/narrow: When vibrato is referred to as wide or narrow in guitar playing, this is a reference to how much tension is placed on the string. Generally speaking, bigger sounds need a wider vibrato width or higher tension, while soft sounds need a lower tension or narrow vibrato.
Whammy Bars and Sound Physics
Another accessory on electric guitars that is used to manipulate the soundwaves generated by the instrument is the whammy bar. Whammy bars are an alternative to playing the guitar with manual vibrato on individual strings. These devices are located at the guitar’s bridge and serve to modify string tension and pitch via a controlling lever. Whammy bars are often incorrectly referred to as tremolo bars.
The Difference Between Vibrato and Tremolo in Sound Physics
When you start to learn about the modification of pitch on an electric guitar, you’ll probably hear references to both vibrato and tremolo. While vibrato creates expression in a note by modulating the pitch of the soundwave being generated, tremolo creates expression in a note by modulating the volume of the soundwave.
Rather than using a control lever, tremolo is manipulated in an electric guitar’s sound through either a step pedal input or through built-in components in the guitar amplifier.
The large number of ways that a guitar’s soundwaves can be affected by both physical and electrical manipulation is what has led to the electric guitar’s popularity in musical forms across the world. From rock and roll and country to jazz and metal, it is arguably one of the world’s most versatile instruments.
Other Factors That Affect Electric Guitar Sound
Along with the techniques that guitar players use to deliberately manipulate the soundwaves generated by their guitars, there are also other factors that can influence how the guitar sounds. Not all of these factors have to do with the guitar itself—some also originate from the amplifier. Some are deliberate, and others are the result of malfunctioning equipment.
Here are a few physical effects that can change the sound quality of an electric guitar:
- Distortion: Distortion is a common sound effect found in electric guitars and can come from several sources such as a torn speaker front, a rack effect, or a stompbox pedal. These things cause the guitar’s sound to be distorted or “dirty” when it comes from the amplifier’s loudspeaker.
- Overdrive: Overdrive is a name for the specific distortion caused by turning up an amplifier too high. While distortion effects can come into play regardless of how loudly the guitar is being played, overdrive effects are directly linked to the volume of the instrument.
- Fuzz: Fuzz is caused by heavy saturation in the guitar signal (usually induced by multiple transistors) until the tone of the guitar note becomes fuzzy with a long sustain. Sustain is the lingering vibrations left after a guitar’s string is plucked or struck. Fuzz is typically generated using devices known as fuzz boxes.
Some of the most famous rock and roll bands in the world have historically used various forms of distortion and effects to manipulate the sound of their guitars to generate complex music. However, these terms are also used throughout the music industry by sound editing professionals to indicate the overall quality of an electric guitar’s audio signal in a recording.
How Do Electric Guitars Work? Final Thoughts
Electric guitars are a masterwork of physics.
Even dating back to their humble beginnings in the early 1980s, electric guitars have always been one of the most advanced pieces of musical technology when it comes to producing varied and colorful sound. Few other instruments in the world combine the complex factors that go into the physics behind an electric guitar. We hope that this article serves as a helpful guide to help you understand the physics behind guitars.
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