Noise Suppressors/Noise Gates

I have a DOD multi effects processor that has a noise gate. You will probably have more controll with a stand-alone pedal. My effects processor has 3 levels to choose from and thats what it does. It keeps reverb and hum from happening at those moments when not playing. You could avoid using one by just palm muting or such. You just have to make sure you set it low enough that it doesn't kick in when you don't want it to. Like if you hit that long ringing power chord and just let it ring and ring and ring, at some point the signal will decay to the level you have set and it will clip your sound.