Feedback is that ultra annoying shrill you hear when your gear gets criss-crossed with itself...
Not your chance to let me know how much you are enjoying the site so far.
In addition to being crazy loud, it can damage your speakers and your ears.
It occurs when the output from an amplified source is re-introduced (fed back) into the input- causing an amplification loop.
Despite how bad it sounds, this is known as constructive interference...though you may argue the result isn't constructive at all.
You can think of it like how a tidal wave is made in the bathtub.
If you push your body back and forth with a certain rhythm, the water will start to follow you. Each cycle (or trip back in forth in the tub) adds more energy to the system until...
BOOM! There is a massive (relatively speaking) tidal wave that spills over to the floor.
What do you mean I must be the the only one who's done this?!?
Ok, let's get back to what goes on in the studio.
This commonly occurs when the output of your speakers or monitors gets back into the input of your microphone.
The easiest way to fix this is to simply move the mic farther away from the speakers as this phenomenon is highly dependent on distances.
Another option is to position everything carefully so that the speakers don't project to where your mics are sensitive, or what I refer to as the "Danger Zone".
Although you may get on the Highway to the Danger Zone... but you should not actually go there.
It's a Top Gun reference - try to keep up.
Some guitar preamps have something called a notch filter which can be adjusted to prevent the feedback-causing frequencies.
This is almost exclusively a live music problem... therefore it is not our problem for our purposes here. If you remember one thing let it be this:
Do not close the loop.
Feedback loops are super loud and will make you think you are going to surely die from the audio blast you will receive.
Now let's light the fires and kick the tires!