Noise Gate/Expander

Noise gates and expanders are volume-based plug-ins and the first of a few advanced plug-ins I’ll cover.

These two plug-ins are part of a special group of volume-based plug-ins called “dynamics processors,” one of which I covered early on in this series: the compressor. In a sense, the noise gate and the expander are cousins of the compressor.

Dynamics processors are called such because they control dynamic range. Remember, dynamic range is the difference between the loudest and softest parts of a piece of audio, so dynamics processors work by compressing or expanding this gap.

As opposed to a compressor, which decreases the dynamic range of a track, noise gates and expanders do just the opposite; they increase dynamic range. Because of their similarity to other dynamics processors, noise gates and expanders will have many of the same parameters: “threshold,” “ratio,” “attack,” “release,” and “gain.”

Since I’ve explained these parameters before, I’ll just go over some of the differences between compression and expansion.

The threshold of a noise gate or a limiter determines the level under which, as opposed to over which, the plug-in will begin to work. When the level of the track falls below this number, the volume will be reduced by a particular amount, thereby increasing the gap between the loudest and softest parts of the audio.

The ratio determines the amount by which the volume will be reduced when the track’s level falls below the threshold.

A noise gate works by the same mechanism as an expander, but it will have a parameter called something like "reduction," instead of a ratio, which determines a specific decibel amount by which to reduce the volume when it drops below the threshold. A “reduction” of -100 dB, for instance, will practically silence the track when the gate is activated, while a “reduction” of -10 dB will reduce the audio by exactly 10 dB, regardless of how far below the threshold the volume drops.

Noise gates and expanders come in handy when the dynamic range of a track is too small, when there is not enough of a gap between the loudest and softest parts. In some cases, an expander will accentuate the peaks and give life to a track by reducing the softer parts of the audio. In other cases, a noise gate might be used to completely silence unwanted noise between the peaks. This is a common practice when working with recorded drums.

Whatever you need them for, noise gates and expanders are important studio tools to understand and keep in mind, especially once you’ve got the hang of mixing basics.