Gate

An Audio Gate or Noise Gate is another dynamics processor that works kind of opposite from a compressor. A gate uses the threshold to decide which information should be turned off, so if the signal is loud and above the threshold it is unaffected. Once the signal becomes soft enough to drop below the threshold it is completely cut off. This is commonly used with guitar tracks to turn off amp noise while the guitar is not playing and mics on drums to turn off bleed from the rest of the kit when the specific drum is not being played. Gates can also be used to create very cool effects especially when triggered by a sidechain.