software

What exactly do these do? My understanding was that they quieted the excess noise generated from having a long chain of pedals, but my friend says he can use one to make his amp feedback less. So what's the deal? What does it actually do?

-X

I had the same understanding as yours, but I found out that it is wrong. It's true that a noise gate eliminates the excess noise, but it does that only when the gate is active. When the signal reaches certain decibel level, the gate opens and then you have the quot;signalquot; and the excess noise as well.

A device that trully eliminates the excess noise can be an EQ, preferably a parametric EQ, or a noise eliminator. I think that Rocktron created a true noise destroyer and Behringer created feedback eliminator. What these devices do is that they focused on a particular frequency or a range of frequencies that causes the excess noise to be apparent or generates feedback.

The negative part of using these devices improperly can be problematic. For examples: a noise gate with high threshold can shorten your sustain; and a noise destroyer or feedback eliminator can alter your sound, because the frequency that they target plays its own role in your sound, so your sound may become less bright or lose attack or etc.

I think there is another type you can add to the list too, a limiter.

A noise gate will completely shut off all sound when it reaches a certain level

An EQ/parametric EQ will just alter the frequency. This can be used to eliminate unwanted frequencies by 'notching' them out. But it still alters your overall sound.

A limiter is can be similar to an EQ I suppose, and will eliminate any frequencies above/below a certain level.

I thought a Noise Gate kept the little noises from escaping from the yard.