Can You Automate Compression?

In recording and processing audio digitally, we rely on various tools to help up get to the desired goal.

One important tool in audio processing is called a compressor.

This is a term you’ve probably come across a number of times if you’re a music producer or sound engineer.

Compression is simply a tool for controlling dynamic range.

This post will discuss whether compression can be automated because it is a topic that I see on most audio production forums. Therefore, I’ll shed some light and hopefully answer people’s questions regarding this.

With that said, can you automate compression?

Just like most effects, compression can also be automated and applied to specific elements in a mix, at a specified sections, with specific instructions.

It’s all a matter of choice, there’s no rule.

Compression parameters

Below, I’m going to walk you through parameters that can be found on compressors and how you can automate them to your liking.

Threshold

First things first, the threshold parameter simply sets the level at which the compression effect should kick in.

This means that only when a level passes above the threshold will it be compressed.

If the threshold level is set at say -12 dB, only peaks of the signal that go above above that level will be compressed. The rest of the time, no compression will be taking place.

If you therefore find it useful to change the level at which you want your compression to kick in, you can can automate the threshold to the said level.

Knee

The knee is simply how the compressor transitions between the non-compressed and compressed states of an audio signal passing through it.

Compressors usually offer switchable choices between a soft knee and a hard knee setting.

Some compressors will even allow you to control the selection of any position between the two types of knees to offer you the option of a balance between soft and hard.

With automation, you can choose parts of your mix which you would prefer to use soft, hard or a balanced form of knee to control the transitions between compressed and non compressed.

This kind of compression automation can be useful for instruments when you’re looking to make it sound more realistic  and less robotic.

Attack Time

The attack time is simply the time it takes for the signal to become fully compressed after going overthe threshold level.

Faster attack times are usually between 20 and 800 ms (microseconds) depending on the type and brand of the compressor.

 Slower times generally range from 10 to 100 ms (milliseconds).

Some compressors express this in terms of slopes in dB per second rather than in time.

If you look to automate the attack of a compressor you’ll basically have control of how quickly your compressors compresses the signal when exceeds the threshold.

Automating compression attack times can be useful when looking to decrease the attack time on a certain section of signal whose other parts are generally using fast attack times.

 This can be a great way to eliminate distortion caused by fast attack times.

Release Time

The release time is simply the opposite of attack time.

Release time on a compressor is the time it takes for the signal to go from the compressed state back to the original non-compressed signal.

Release times will be considerably longer than attack times, generally ranging from around 40-60 ms to 2-5 seconds, depending on which compressor unit you’re using.

It’s a lot more practical to have shorter release times without producing a “pumping” effect, which is caused by a cycle of the compressor going through activation and deactivation.

In times where you need longer release times it may be helpful to use compression automation on certain sections of your mix in order to avoid what is called the breathing effect which is what happens when your dominant signal modulates the noise floor.

Compression Ratio

Compression ratio specifies the amount of attenuation applied to the signal. Attenuation is just a fancy word for reduction.

So, ratio simply specifies the amount of reduction applied to the signal.

There are a wide range of ratios available depending on the type  compressor you are using.

A ratio of 1:1 (one to one) is the lowest and it represents “unity gain”, or in other words, no attenuation or no compression at all.

Compression ratios are expressed in decibels, which means that a ratio of 2:1 means a signal exceeding the threshold by 2 dB will be attenuated or reduced to 1 dB above the threshold, or a signal exceeding the threshold by 8 dB will be attenuated down to 4 dB above it, etc.

A ratio of around 3:1 is what is usually considered moderate compression, 5:1 would be medium compression, 8:1 starts getting into strong compression….

Above 20:1 is generally considered “limiting” by most, and is used to ensure that a signal does not exceed the amplitude of the threshold.

With automation, you could play around with ratio at various sections of a mix if you feel the need to reduce a signal a certain way.

Output Gain

In as much as we perceive compressed signals as being louder, compression-induced attenuation actually lowers the output. You can notice this if you pay close attention.

 This is where “output gain” or “make‑up gain” or simply “gain” comes into play.

It’s main use is to compensate for the reduction of the audio signals volume by a compressor.

In short, it “makes-up” for the attenuation done by the compressor.

By using compression automation, make up gain can be an effective way to deal with certain quite sections that you may spot.

You can use your automation to either reduce or add some gain to the section.

Final Thoughts

You can certainly automate compression and it may actually be a handy tool to make specific adjustments to certain parts or sections of a mix.

As a caution,

Ensure that you carefully plan how you’re going to go about automating your overall compression or its parameters.

Automating compression requires some careful planning, calculation and execution.