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What is Audio Compression: Everything You Need to Know

what is audio compression
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Audio compression is one of the most confusing topics for beginners and for more intermediate producers.

So in this article, I’m going to explain it in really basic terms for you.

Let’s get into it.

What Is Audio Compression?

A compressor is a tool that helps you to make the volume of something more consistent.

I can explain…

For example, let’s say we have a vocal recording, the difference in volume between the quietest part and the loudest part is called the dynamic range.

Vocals by nature have a really large dynamic range, which means if a vocal is in a song and it’s not being compressed then the loud parts are going to poke out and be too loud whereas the quiet parts will get lost underneath the rest of the music.

So, to even this out we need to use compression on those vocals to reduce the ‘dynamic range’.

How does audio compression work?

So to understand how compression work, we need to go through its five main controls.

Threshold, Ratio, Attack, Release, and Gain.

Threshold

The Threshold is the volume that you set that you want the vocal or recording to stay around and when the vocal goes over this it gets compressed.

Ratio

The Ratio allows you to control how much the compressor reduces the gain once the signal passes the threshold.

The numbers on the ratio knob represented the ratio of input to output. The higher the first number,  the more extreme the compression. If it sounds confusing check the image below.

what is audio compression : Threshold
image source: https://themixingtips.com/

Attack and Release

Attack time is the time taken for the compression to take effect and it’s measured in milliseconds.

for example, if the attack is set to 20 milliseconds, the compression starts to work 20 milliseconds when the signal goes over the threshold.

The Release is the opposite of attack, it’s the time it takes for the compressed signal to return back to its own uncompressed original state once the signal has fallen below the threshold.

what is audio compression : Attack and release
image source: https://www.pro-tools-expert.com/

Gain

Finally, Gain or make-up gain is added volume that we apply in order to bring the quieter parts of the audio up after we’ve brought the louder parts down to make the volume more consistent overall.

How to use Audio compression?

Using compression can be tricky when you first start mixing.

Unlike other audio effects such as Delay and Reverb, you may find it difficult at first to hear the subtle tonal differences that a compressor is supposed to give you.

It was like that for me and for many of the best producers, engineers, and mixers in the world.

The best way to improve with compression is by practicing and having a clear goal when applying it.

Here are some tips to help you set the compressor knobs correctly to get the sound you want.

Audio Compressor

Attack=Punch

As mentioned earlier, the attack knob is one of the five main compressor controls.

Now when you’re thinking about attack time, a great shorthand way to simplify what the attack knob actually does is to think about it in terms of punch, or impact.

Slow Attack Time allows the initial punch or impact of notes or hits to pass through the compressor before the compressor clamps down on a sound, and that’s going to accentuate the punch or the impact of a sound.

So if you want to make something sound punchier and more impactful try going with a slow attack time.

Fast Attack Time is going to turn down punch and impact resulting in a sound that sounds softer and much less impactful

So if you have a track that sounds a bit too punchy, maybe you want to soften it out a little bit, you want to kind of push it back in the mix so it’s not too aggressive, then using a fast attack time will give you that.

In this case, it’s about having a clear objective, right?

Release=Low level detail

One way to simplify thinking about the release time is to think about it as a control that allows you to determine how much of those low-level details, those quieter moments in a track, get brought up.

Fast Release Time is going to tell the compressor to let go very quickly.

The result is that a lot of the low-level stuff in the track/the quieter parts will come up and become much louder.

For example, if you’re compressing a vocal and you want to bring up a lot of the vocal’s detail, the tail ends of the phrases, the quieter breaths then setting a fast release time will allow you to do that.

Slow Release Time is going to tell the compressor to let go very quickly.

On the other hand, if you don’t want to bring up a lot of that low-level detail and you want the compression to just kind of control the track, setting a slower release time can give you that type of effect.

Ratio=Intensity

The ratio is a control that essentially determines the aggressiveness or intensity of the compressor.

So if you have tracks that are wildly dynamic and you really want to rein things in, higher ratios will allow you to do that.

however, lower ratios are going to be much more transparent, natural, and gentle.

Conclusion

Using compression can be tricky when you first start using it but the best way to improve with compression is to keep practicing and to have a clear goal when applying it.

Have a question? Let me know in the comments below. I’ll try my best to answer all of them.

For more articles like this check our website Producers Routine.

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  1. Pingback: 5 Types of Audio Compressors You Need to Know - Producers Routine

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