Guitar feedback is typically an unwanted, uncontrollable mess of high pitched screaming and chaos. It can be great to create cool effects if you’re able to control it, but most of the time we’re trying to kill it as much as possible.

It can ruin a performance in an instant, and knowing how to stop it is an essential skill for any player.

If you’ve ever played a hollow, semi-hollow, or acoustic guitar you’ll notice that there seems to be an increase in just how susceptible you are to feedback compared to a traditional solid body instrument. But why is that?

We’re going to look at the science behind these issues and help you minimize unwanted feedback so you can still play your favorite hollow or semi-hollow instrument night after night.

What Is Feedback?

Feedback – also known as a feedback loop – is an audio phenomenon where the signal being outputted and the source capturing that output feed into each other continuously. For example, feedback can easily be created by cranking up your amplifier and then standing directly in front of it.

What’s happening can be broken down into 3 events:

1) You play a sound on the instrument

2) The pickups capture that sound and send it to the amplifier

3) The amplifier spits out that sound through the speaker, back into the pickup again

We’ve created a loop of audio that will continuously make a sound because the input and output “feedback” into each other over and over again until the loop is broken.

Not only that but if you’re running a loud amplifier or anything that would compress the audio (a compressor or even distortion/overdrive) you’re just adding to the problem.

Any guitar is susceptible to this phenomenon given the right circumstances, but there’s a particular reason that hollow and semi-hollow instruments are far more sensitive to this.

Acoustic Feedback

We know what a feedback loop is, now we need to know about “acoustic feedback.”

Acoustic feedback occurs when sound waves enter the instrument itself and bounce around, causing the body to resonate. This resonance then causes the strings to resonate, which creates more sound that is then received by the pickups, which come out of the amplifier, which outputs into the body, and the circle is complete.

This is only an issue when plugged into an amplifier because sound waves created by a guitar – acoustic or electric – are only loud enough to make a sound and then decay over time. Sound waves get weaker as they bounce, so without amplification to constantly raise the overall volume and create that cyclical effect, you don’t have any problems.

In short, the volume is the key contributing factor to feedback.

While hollow or semi-hollow instruments are impacted by acoustic feedback, solid-body guitars are only impacted by the part of the loop created through amplification. It’s one less factor in feedback, making a solid body much more resilient.

Killing It Swiftly

If you want to prevent these issues from occurring, you’ve got three variables to manage:

1) Lower The Volume

By keeping the volume knob down on your amp you are minimizing the amount of sound being pushed back into your pickups, which allows you to break the chain and prevent a loop from being formed.

Alternatively, you can manage volume by simply moving away from your amplifier which will have the same result through creating space instead of adjusting your amp.

The second method is especially helpful if you find your amp sounds better at a particular volume, you want to achieve natural amp overdrive without having to use an attenuator, or you’re playing a show where you don’t have access to cabinet microphones to boost the volume for you.

2) Lower The Gain

The more gain and compression you add to your signal the less dynamic range it has. This means the quieter notes aren’t going to be as quiet anymore.

One reason we choose to compress a guitar tone is to add sustain by minimizing the difference between our quietest and loudest notes, letting notes last longer at a particular volume level.

As you probably guessed, that also means feedback that passes the threshold will also stick around for longer and get created more quickly. Distortion and overdrive have the same compression effect as a clean compressor does.

Of course, many will object to turning off your favorite overdrive pedal and we tip our hat to those individuals, but we have to share the tip regardless!

So What Now?

Don’t let the idea of feedback stop you from purchasing the guitar you really want, but before pulling the trigger make sure you understand the pros and cons of each body type and ensure that your dream instrument is still in line with its practical applications.

You don’t see hollow body guitars in jazz because metalheads hate the look of them, it’s because they aren’t as practical in high-gain music.

If you’re still not budging on that semi-hollow Telecaster you’re dreaming of, no worries. Use our tips to help yourself out. If that’s not enough, take a look at some interviews with artists like Allan Holdsworth, Tom DeLonge, or Tim Armstrong about managing feedback with high-gain tones and semi-hollow instruments. It’s hard, but don’t think it can’t be done!

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