A noise gate is a pedal that, when active, will reduce unwanted noise in your circuit. By ‘noise,’ we typically mean hum, hiss, or buzz generated from your guitar, other pedals, or amp itself. This is sometimes caused by different gain stages that introduce noise into the circuit or external electrical signals interfering with your sound.
One of the best ways of understanding how a noise gate works is to explain it in a real-world scenario. Consider somebody banging on your door, and you’ll only open it and let the person through if they bang loudly enough – if it’s too quiet, then you don’t open the door. In a noise gate, if your guitar signal reaches a certain ‘threshold’ – a term you will hear come up frequently when referring to noise gates – it is allowed through the gate. As it becomes quieter, the gate – or, in our scenario, your door – closes and stops any other sound coming through. This is a noise gate in its simplest form, and the addition of parameters such as ‘hold’, or ‘release’ can have a vast impact on how the gate reacts, which makes them more or less suitable for specific playing styles or genres.
The noise gate should always come after where the noise emanates from in your signal chain, so typically after a distortion or fuzz pedal. Many choose to have it near the end of a signal chain but prior to any reverb or delay pedals, as the gate can interact poorly with the repeats, cutting them off prematurely. A gate can also go in your effects loop with your time-based effects, and this may be preferable if you want to remove some noise from your preamp if you have a particularly heavy gain tone driven directly from the amplifier.