EQ & Dynamics
What is a noise gate? How gating works and when to use it
On this page15 sections
A noise gate mutes or reduces a signal when its level falls below a threshold you set. When the level rises above the threshold, the gate opens and audio passes normally.
That is the whole idea, and it explains the single most important limitation: a gate only works in the gaps. While the wanted sound is playing, the gate is open, and everything else on that channel is open with it.
What a gate is genuinely good at
- Silencing the hum, hiss or room tone between phrases and hits.
- Removing microphone bleed from other instruments in the gaps — the hi-hat in the snare mic between snare hits.
- Tightening a room-recorded drum kit by cutting the ambience between hits.
- Cleaning up an amp’s noise floor while nobody is playing.
Notice what they have in common: the unwanted sound is louder than nothing but quieter than the wanted sound, and there are gaps.
What a gate cannot do
- Remove hiss from underneath a sustained vocal note.
- Remove bleed while the source is playing.
- Fix a noisy recording where noise and signal are similar in level.
- Make a badly recorded source sound clean.
If the noise is present during the sound, you need a denoiser, not a gate. Noise gate vs denoise covers how to tell which problem you actually have.
Every control, explained
Threshold
The level that decides open or closed. This is the main control and it determines everything else.
Set it from the quietest wanted sound, not from the loudest noise. If the quietest note fails to open the gate, that note disappears — and that is the most common gating failure.
Attack
How quickly the gate opens once triggered. Fast attack preserves the transient at the start of a sound. Slow attack softens the entry, which can remove clicks but can also swallow the initial hit of a drum.
Hold
A minimum time the gate stays open after triggering. This bridges small dips inside a sound so the gate does not flutter mid-note.
Hold is the underused control. Adding a little of it fixes a lot of erratic gating.
Release
How quickly the gate closes once the signal falls back below the threshold.
Too fast and you chop the decay of every note. Too slow and the noise you were removing stays audible after every sound. Release is where a gate goes from useful to obviously artificial.
Range or depth
How much attenuation the gate applies when closed. A gate that closes fully produces digital silence; a gate with a limited range only reduces by a set amount.
Limited range usually sounds more natural, because the room tone dips rather than vanishing. Full closure suits tightly produced material where silence is the intended effect.
Hysteresis
Separate thresholds for opening and closing, with the closing one lower.
This stops chatter — the rapid open-close rattle that happens when a signal hovers right at the threshold. If your gate stutters, hysteresis is the fix, not a higher threshold.
Detector filtering
Filters applied to the detection signal, not the audio you hear. This lets the gate trigger on the useful part of the source while ignoring the rest.
The classic case is a snare gate: filter the detector to the snare’s core frequency so the hi-hat bleed no longer opens it, while the audible snare keeps its full frequency range.
Lookahead
The gate delays the audio slightly so it can open just before the sound arrives, preserving the transient without needing an extreme attack. It costs latency.
Gate, expander, or edit?
| Situation | Best tool |
|---|---|
| Consistent noise in obvious gaps | Gate |
| Subtle noise reduction with natural transitions | Downward expander |
| A handful of noisy spots | Manual editing or clip gain |
| Noise under the wanted sound | Denoiser |
| Removing bleed while the source plays | Nothing — re-record or re-arrange |
On an exposed lead vocal, manual editing frequently beats a clever gate, because you can make an intentional decision at each phrase. On thirty drum tracks, a gate is the only realistic option.
A quick setup method
- Set range low at first — a moderate reduction, not full silence — so mistakes are audible.
- Raise the threshold until the gaps clean up.
- Play the quietest wanted sound. If it does not open the gate, lower the threshold.
- Add hold until flutter inside sounds stops.
- Lengthen release until note decays survive.
- Add hysteresis if it still chatters.
- Filter the detector if the wrong sound is triggering it.
- Finally, decide whether the range should go deeper.
For the vocal-specific version, with all the traps that come with consonants and breaths, read how to gate vocals without cutting off words.
Where the gate belongs in a chain
Usually first, or very close to it. Gating before compression means the compressor’s makeup gain does not raise the noise you were about to remove.
Sometimes the reverse is better: a wildly dynamic source can trigger more consistently after gentle levelling. Test both — see effects chain order.
The plugin
SPC Gate covers this as a focused tool: linked stereo detection, hysteresis, hold, and exact digital-zero closure when hard silence is what the production wants. SPC Vox includes gating alongside the other vocal cleanup stages when the job is a whole voice chain rather than one gate.
Frequently asked questions
What does a noise gate do?
It reduces or mutes a signal when the level falls below a threshold, and lets it through when the level rises above it. That removes noise in the gaps between sounds. It does nothing to noise that occurs while the wanted sound is playing.
What is the difference between a gate and an expander?
A gate applies a fixed amount of attenuation once the signal falls below the threshold. A downward expander reduces level proportionally, so the transition is gradual. Expansion usually sounds more natural for subtle cleanup.
Why does my gate cut off the end of notes?
The release is too fast, the threshold is too high, or there is not enough hold time. Lengthen release and add hold so the gate stays open through the decay of the sound.
What is hysteresis on a gate?
Hysteresis makes the closing threshold lower than the opening threshold. Once the gate opens, the signal has to fall further before it closes, which stops rapid open-close chatter when the level hovers around one value.
Can a gate remove background noise from a recording?
Only between sounds. While the wanted sound is playing the gate is open and the noise passes with it. Continuous noise underneath the material needs a denoiser, not a gate.