Acoustic guitars have sound holes to increase the vibrations (resonance) transferred from the strings and reflected in the guitar’s body. They also help in the feedback process when the guitar is amplified.
In this article, I’ll discuss the physics of why acoustic guitars have holes, and how to develop a guitar that sounds better.
So without further ado, let’s begin.
How does a guitar hole work?
The use of a sound hole in guitars boosts the efficiency of sound radiation at low frequencies.
The soundhole, by vibrating both the volume of air within and near to its aperture, improves the radiation of sound.
A guitar’s top or soundboard is designed and constructed in such a way that it vibrates like a membrane excited by energy from inside (the pickups).
The resulting vibration has both lateral and longitudinal components.
The lateral vibration contributes to the sound of a guitar, but it is weaker than the longitudinal waves.
The sound size of the hole is chosen so that it will support strong vibration at frequencies where both modes are fairly well excited.
For example, an opening about two-thirds as long as the wavelength of maximum energy in the lateral mode is typical for guitars with a wide range of string lengths (the length from nut to bridge) and a wide range of string densities.
The size and shape of the soundhole is also related to how efficiently it can radiate low-frequency energy, which is important for bass guitars.
A guitar hole works by allowing air within its volume to resonate in sympathy with the string’s vibration (the longitudinal waves).
It does this by being open to the air, rather than by “pushing” on it.
Does a hole in a guitar affect the sound?
The soundhole itself doesn’t affect the sound of your guitar.
However, it does affect your guitar’s tone by changing how long it takes for low frequencies to get out of the body and into your ears.
The opening acts as a waveguide that transmits energy from the inside (the strings) through its edge in phase with later
It is more the soundboard of your guitar than the hole itself that actually creates your guitar’s sound.
How big should a soundhole be?
When it comes to the size of your soundhole, it’s all about how much resonance you want.
If you’re looking for good tone and sustain, then a smaller hole is better because it keeps more low-end in the body.
On the other hand, if you need your guitar to project well without sounding too boomy (unwanted low frequencies), then a larger hole with more edge cutaway is better.
A bigger soundhole also helps if you’re going to be playing the guitar with high gain because it makes sure that feedback doesn’t occur as easily, and allows for less damping from the player’s hands on either side of the body.
The size of the soundhole depends on the size of the guitar and what you’re going to use it for.
4″ soundholes are standard on dreads and jumbos. The majority of small-bodied guitars (such as OM’s) have smaller soundholes.
Does the size of a soundhole really matter?
The larger the soundhole the louder the volume of the guitar.
The size of the soundhole will determine how much volume and bass you can get out of your guitar.
A bigger hole also means more low end, which is good for blues players who want to make their guitars louder without making them too boomy (too many unwanted low frequencies).
On the other hand, if you don’t want that much low end, then a smaller hole is better because it’ll keep the sound of your guitar more intact.
Larger holes are also helpful for projecting guitars without sounding too boomy (unwanted frequencies), and they help prevent feedback when playing with high gain.
The size of the opening will depend on what you want to use the guitar for.
Smaller soundholes are standard on small-bodied guitars, such as OM’s and smaller jumbos.
The majority of dreadnoughts have larger holes because they produce a lot more low end which works well with their big size.
Other factors that affect volume include:
- String length and density
- Body size/shape (the bigger the body, the more volume it’s going to produce)
- Body woods (the denser and thicker your wood is, the louder it’ll be)
- The shape of an acoustic guitar soundhole affects tone.