What is a Noise Gate in Audio(Is it the as Noise Reduction)?

by ReverbLxnd in Mixing

What is a noise gate in audio engineering and music production? What is the difference between noise gating and noise reduction and when do you use each?

Today I want to talk about reducing noise in your audio.

We will discuss what a noise gate is and how you use it to improve the clarity of your recordings. We will also clear up some misunderstandings in the difference between noise gating and noise reduction, which are two entirely different things.

Everything we’ll talk about here works in any DAW, and it also relates to live sound.

Let’s dive right in.

What is a Noise Gate?

A noise gate is an effect you add between the audio source and the recording. You can use either a hardware noise gate or, more commonly, a plugin in your DAW. Most DAW come with noise gate a stock plugin.

The main function of a noise gate is to eliminate sounds below a given audio threshold or level, not to reduce noise from a recording.

A noise gate allows a signal to pass through only when it is above a set level. As long as the audio level is above the set threshold, the gate is open. If the signal falls below the threshold, the gate is closed.

It is called a noise gate because every audio signal contains some noise.

The noise can be generated by the electrics or captured in your recording environment, or be introduced in your signal by a raft of several other ways.

How to Use a Noise Gate to Improve the Clarity of Your Recording

This is a 4-step process—

  1. First you create the audio track and record what you want at a good average signal level.
  2. Next, add a noise gate plugin to the track. Most DAWs will have this as a stock plugin.
  3. Adjust the threshold level so that it cuts the audio when there is only noise present. If you set it too close to your recording level, it might cut some of your good audio signal.
  4. Set the attack and release times. We’ve discussed the attack and release times extensively in this blog but for a gate plugin, the attack time is how fast the gate starts to work counting from the time the signal passes below the threshold and the release time is how fast the gate opens again when the signal returns above the threshold level. You can adjust these settings until you are satisfied with the result.

Noise Reduction vs Noise Gating

My favorite way, by far, to remove noise from a recording is noise reduction.

With noise reduction you use various software DAWs and plugins to scan the noise in a recording and then apply various filters and processing to reduce that noise.

You end up with an original and processes recording with the noise reduced. We say the noise reduced recording is denoised.

After comparing the original and denoised recordings, you should be able to hear quite clearly that the noise has been reduced across the entire recording.

Noise reduction is perhaps the best technique for anyone doing something like a podcast or recording vocals or guitar because it completely eliminates that static hiss in the background.

The problem however, is that a lot of people argue that the noise reduction process in too complicated.

Why not just use a noise gate?

The trick is in understanding how a noise gate actually functions.

A noise gate doesn’t actually reduce the noise in a recording at all, it only cuts sound that exceeds a certain set threshold. If the noise doesn’t exceed the threshold, it left in.

As long as sound doesn’t close the threshold, it lets everything through — your voice, the guitar, the noise, all of it.

A noise gate will cut some noise out but you’ll still leave in tons of noise compared to a denoised recording where you’ll end up with a lot less backrground noise.

This distiction seems to be a topic that crops up more and more because many beginners reach for a noise gate when what they areally need is noise reduction.

You have to realize for getting rid of noise a noise gate doesn’t necessarily do an awful lot. You’ll likely be still unhappy or unsatisfied by the amount of noise in your recordings when using a noise gate as opposed to a noise reduction.

What then are the uses of a noise gate?

Well, noise gates are extremely useful in certain situations.

Common Usecases for a Noise Gate in Recording

Noise gates are particularly useful in filtering out room noise and feedback loops with live sounds.

Imagine you’ve got a singer in stage and a instruments playing. When the singer is singing, that’s fine, when they stop singing, you need to cut that mic out because you don’t want the guitars, drums and other room noise coming through the mic and cause all sorts of feedback loop.

So in live sounds, noise gates are usually essential.

With vocals vocals, noise gate helps you get clean separation between words and phrases.

You have to be careful though with vocals because you can easily cut out all the breath sounds in vocals, they add an important human quality to the recording.

Noise gates are essential with extremely high gain guitar tones because when using heavy distortion, you will get a lot of noise from the boosted levels.

When you are playing the guitar, it’s fine, you can have the noise in there so that it’s huge and distorted. But when you stop playing, you need a noise gate to cut out all that static hiss and hum from the amp because you don’t want that to be picked up.

Another use case is with drum kit separation.

If you are hitting a snare, you don’t want your snare mic to pick up all the other drums. So you have a noise gate setup for that so that it gives you a really cleaner punch.

With acoustic instruments you’ll typically get a lot of room noise in. A noise gate can be just the thing to bring out only your instrument in the recording but perhaps, it’s better to use noise reduction to pull all that noise out.

In the studio, noise gates are not actually very useful because you might as well just trim your audio and just cut out all the noise on the audio anyway.

If you have a particularly noisy recording, I would recommend either cleaner re-recording or using noise reduction technique.

Even if you have a hardware noise gate, they do a really good job but they function the same as the software or plugins. You’re still going to have all the noise coming through above a certain threshold.

The last thing I want to mention is that you need to be careful when you are using a noise gate or denoising not to do it too much There is a bit of noise that is actually fine (such as some of the breathy vocals I mentioned earlier).

If you push the denoising or noise gating software too far, it will sound too filtered, which never sounds nice.

In such a case, cutting back should let you find the sweet spot in the middle where, for instance, you can still retain a lot of the nice quality of the guitar without ruining the signal with over-processing.

Hopefully that clears up that misconception.

In Conclusion

The key takeway here is that — with a raw signal you’ve got noise and signal, with noise gate you’ll still have the signal and noise in it but cut off the sides, whereas with a full denoising software you are actually reducing the noise in the entire signal.

Sometimes, a bit of noise is fine. How much, is totally subjective. It’s up to you to decide how much is too much.

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That’s it for this article.

ReverbLxnd

I've been a musician and brought in my stuff for mixing and mastering, I've been my own producer where I wrote, recorded, mixed and sold my own stuff. Now, I'm *mostly* an audio engineer, where I only record and mix for clients. I'm currently based in Berlin, Germany, where I operate ReverbLand out of. Got a question? DM me on Instagram or Twitter @reverblxnd everywhere, or shoot me an email reverblxnd@reverbland.com. I'd love to hear from you.

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