Noise Gate

In-Depth Explanation

Noise gate is a dynamic processor that mutes or reduces an audio signal when it drops below a set threshold. When the signal is loud enough, the gate opens and the audio passes through. When the signal gets quiet, the gate closes and silences the audio. This removes background noise, bleed, and unwanted sounds between the moments you want to hear.

How Noise Gates Work

A noise gate is the opposite of a compression plugin. A compressor turns down the loud parts. A gate turns down the quiet parts. Both use a threshold to decide when to act.

When the input signal rises above the threshold, the gate opens. Audio passes through at full volume. When the signal drops below the threshold, the gate closes. The audio is attenuated by a set amount (called the range). A range of -80 dB effectively mutes the signal. A range of -10 dB partially reduces it.

Four parameters control gate behavior:

1. Threshold: The level at which the gate opens and closes. Set it above the noise floor but below the quietest part of the signal you want to keep. If the noise floor is at -50 dB and the quietest vocal phrase peaks at -30 dB, set the threshold around -40 dB.

2. Attack: How quickly the gate opens when the signal exceeds the threshold. A fast attack (1 ms) opens instantly, which is needed for sharp sounds like drum hits. A slow attack (10 to 50 ms) opens gradually, which sounds more natural on vocals.

3. Release or hold: How quickly the gate closes after the signal drops below the threshold. A fast release (50 ms) closes quickly but can chop off the natural decay of a sound. A slow release (300 ms) closes gradually and sounds smoother. The hold parameter keeps the gate open for a fixed time after the signal drops, preventing early closure during brief pauses.

4. Range: How much the gate attenuates the signal when closed. Full gating (-80 dB) silences the audio completely. Partial gating (-10 to -20 dB) reduces the noise without fully muting it, which sounds more natural.

Some gates include a sidechain or key input. This lets you trigger the gate with a different signal. For example, you can gate a bass track and trigger it with the kick drum. The bass only plays when the kick hits. This creates tight, synchronized low end.

Real-World Example

A drummer records a live kit with eight microphones. The snare microphone picks up the snare clearly, but it also picks up bleed from the hi-hat, kick, and cymbals. Between snare hits, the hi-hat bleed is audible and muddy. When the engineer compresses the snare (to add punch), the compressor raises the hi-hat bleed along with the snare. The snare channel becomes a wash of cymbal noise.

The engineer inserts a noise gate on the snare track with these settings:

• Threshold: -25 dB (above the bleed, below the snare hits)
• Attack: 1 ms (instant open for sharp transient)
• Hold: 50 ms (keeps the gate open through the snare body)
• Release: 100 ms (smooth close after the snare decays)
• Range: -40 dB (strong reduction but not full mute)

Now the snare channel is silent between hits. The hi-hat bleed is gone. When the drummer hits the snare, the gate opens instantly and the full snare sound passes through. After 150 ms (hold plus release), the gate closes and the channel goes quiet again.

The engineer then compresses the gated snare. The compressor only sees the snare hits, not the bleed. The compression sounds clean and punchy. Without the gate, the same compression settings would have pumped the hi-hat bleed and made the snare channel unusable.

The engineer used the stock gate plugin in Pro Tools, which costs $0. The same technique works in every major DAW with stock gate plugins.

Why It Matters for Independent Artists

Noise gates solve two common problems for home studio recordings: background noise and microphone bleed. Bedroom producers rarely have acoustically treated rooms. HVAC systems, computer fans, and street noise create a constant background hum. Gates remove that noise during silent passages.

Three practical uses for independent artists:

• Vocal gating: Insert a gate on a vocal track to silence background noise between phrases. Set the threshold above the room noise but below the quietest vocal. Use a moderate attack (5 to 10 ms) and a long release (300 to 500 ms) so the gate does not chop off phrase endings. This cleans up the vocal before compression and reverb.
• Drum bleed control: Gate every drum mic except the overheads. The close mics only pass sound when their respective drum is hit. This gives you a clean, punchy drum mix without cymbal bleed on the snare and tom tracks.
• Guitar amp cleanup: Gate a distorted guitar to silence hum and hiss between riffs. High-gain amps produce constant noise. A fast attack and moderate release silences the noise between chords while preserving the riff.

A warning: gates can sound unnatural if set too aggressively. A vocal that suddenly goes from full volume to dead silence sounds robotic. Use a partial range (-15 to -20 dB) instead of full muting for vocals. This reduces noise without the obvious on/off effect.

For the most natural noise reduction, use an expander instead of a gate. Expanders gradually reduce the signal rather than cutting it off. Most gate plugins include an expander mode. Set the ratio to 2:1 or 3:1 for gentle noise reduction. Read our vocal chains guide for complete gating setups.

Related Terms

• Compression - The opposite dynamic processor, which controls loud sounds instead of quiet ones
• Transient - The sharp initial attack of a sound that gates are designed to detect and preserve
• Noise Floor - The baseline noise level that gates are used to suppress
• Expander - A gentler alternative to gating that reduces rather than mutes the signal