Noise gate

A noise gate or gate is an electronic device or software that is used to control the volume of an audio signal. Comparable to a compressor, which attenuates signals above a threshold, noise gates attenuate signals that register below the threshold. However, noise gates attenuate signals by a fixed amount, known as the range. In its simplest form, a noise gate allows a signal to pass through only when it is above a set threshold: the gate is 'open'. If the signal falls below the threshold, no signal is allowed to pass (or the signal is substantially attenuated): the gate is 'closed'. A noise gate is used when the level of the 'signal' is above the level of the 'noise'. The threshold is set above the level of the 'noise' and so when there is no 'signal', the gate is closed. A noise gate does not remove noise from the signal. When the gate is open, both the signal and the noise will pass through. Gates typically feature 'attack', 'release', and 'hold' settings and may feature a 'look-ahead' function.

Noise gates have a Threshold control to set the level at which the gate will open. More advanced noise gates have more features.

The Release control is used to define the length of time the gate takes to change from open to fully closed. It is the fade-out duration. A fast release abruptly cuts off the sound, whereas a slower release smoothly attenuates the signal from open to closed, resulting in a slow fade-out. If the release time is too short, a click can be heard when the gate re-opens. Release is the second-most common control to find on a gate, after Threshold.

The Attack control is used to define the length of time the gate takes to change from closed to fully open. It is the fade-in duration.

The Hold control is used to define the length of time the gate will stay fully open after the signal falls below the threshold, and before the Release period is commenced. The hold control is often set to ensure the gate does not close during short pauses between words or sentences in a speech signal.

The Range control is used to set the amount of attenuation to be applied to the signal when the gate is closed. Often there will be complete attenuation, that is no signal will pass when the gate is closed. In some circumstances, complete attenuation is not desired and the range can be changed.

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