Noise Gates in Home Recording Music
A noise gate is basically the opposite of the limiter. Rather than limiting how loud a note can get, the gate limits how soft a note can get. The gate filters out sound below the threshold while allowing notes above it to pass through unaffected.
Gates are useful to filter out unwanted noise that may be present in the recording environment. A classic place to use gates is when you record drums. You can set the gate to filter any sound (other drums for instance) except for the sounds resulting from the hits to the particular drum that you have miked.
The following settings are similar to the ones for compressors/limiters:
Threshold: The threshold sets the level (in dB) at which the gate opens (stops filtering the signal). The gate allows all signals above the threshold setting to pass through unaffected, whereas signals below the threshold setting are reduced by the amount set by the range control.
Attack: As with the compressor/limiter, the attack time sets the rate at which the gate opens (in milliseconds). Fast attacks work well for instruments with, well, fast attacks, such as drums, whereas slow attacks are better suited for instruments with slow attacks, like vocals.
For the most part, try to match the gate’s attack time with that of the instrument you’re gating. If you don’t do this well, you may hear a click when the signal crosses the gate’s threshold. This is generally a result of having the attack set too slow for the instrument. Adjust the attack time until this click goes away.
Hold: The hold setting controls the amount of time that the gate stays open after the signal drops below the threshold. After the hold time is reached, the gate closes abruptly. This parameter is listed in milliseconds (ms). The hold parameter allows you to get the gated drum sound that was so popular in the 1980s (Phil Collins, anyone?).
Release: The release setting dictates the rate at which the gate closes after the signal hits the threshold (listed in milliseconds). Unlike the hold feature, the release setting doesn’t close abruptly; rather, it slowly closes (according to the release setting). This produces a more natural sound.
You should set the release time so that it matches the natural decay time of the instrument. Otherwise, you can get a clipped-off sound. (If you want the clipped-off sound, use the Hold feature.)
Range: The range is similar to the ratio setting on the compressor except you choose the amount (in dB) that you want the gate to attenuate (reduce) the signal. For example, a setting of 40dB drops signals below the threshold setting by 40 decibels.