How Acoustic Guitar Works

A brief description of how the acoustic guitar works, how different frets and tunings produce different sounds.

Ultimate Guitar

The Acoustic Guitar, one of the most common and popular types of guitars. Well, how does it work? How are different notes produced? Why do different strings produce different sounds, and why does tuning vary these notes? Why does a guitar sound different than other instruments, even when playing the same note?

All the answers to these questions you'll find in this post.

Q. How does it work?

The acoustic guitar creates it signature sound through the use of cleverly designed hollow body and the fretboard. When you pluck the strings, their vibrational energy travels through the fretboard, into the inner hollow region of the guitar and the vibrations make the air vibrate, producing sound through the opening. This vibration of the air inside makes the whole instrument vibrate, resonating the note you have just played. The back of the guitar also vibrates, but with a lower energy and lesser volume. This effect works better with lower frequencies and as a result they sound louder in the acoustic guitar. Without the fretboard and the hollow cavity design, the strings would vibrate longer, but result in less volume.

Q. How are different notes produced?

Now you may be wondering how does fretting a single string change the note produced, and how do different thickness of strings produce different sounds and finally, how the tuning peg can change the note produced. Well, the answer is pretty simple. Let's try to understand it using the example of a single sting first. Let's use lower E.

Now, the lower E is the thickest string in the standard acoustic guitar. It has a definite weight and a variable tension, which can be adjusted using a tuner. When you pluck it at a particular tension, it vibrates for a certain number of times in a second, producing a particular frequency and as a result a particular note. If you change the tension, you change the amount of energy required for a single vibration and as a result changes the number of oscillations (or you can say vibrations) happening in a second. This changes the frequency, i.e. the note produced. This is how a single string produces different notes while adjusting tuning.

Next comes thickness. You can explain this in the same way, strings of different thicknesses have different weights and as a result require different energies for a particular number of vibrations and same explanation and above. Finally comes length. When you fret a string, you might have noticed that the part of the string above your fingers doesn't vibrate anymore. Thus fretting the strings affects the length of the strings vibrating part and as a result, it changes the amount of energy required to vibrate the length at a particular frequency.

Sounds complex right? Well you haven't even factored in the harmonics or the path of the sound produced. Well, let's get to the final question.

Q. Why do different instruments produce different sounds?

Now the question arises, even when a piano and a guitar play the same note, why do they still sound different. Well, the answer is the path the sound takes and the shape of the sound wave. In a guitar, the sound travels this way :-)

1) The strings vibrate, and the vibrations transfer to the saddle.
2) The saddle vibrates and transfers it's vibrations to the wooden soundboard.3) The soundboard and the body along with the air vibrate and amplify the sound.4) The sound comes out from the hole in the soundboard.

Clearly the path the vibrations take is very different in the case of the piano. This is the reason why the guitar and any other instrument sounds so different even when they play the same note.

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1 comment sorted by best / new / date

    I use 0.13mm strings on a C tuning, sometimes B even, they hold it very nicely and I get that gravely, deep sound that I just adore.