WHAT IS AN AUDIO COMPRESSOR & HOW IT WORKS?
What is Audio Compression?
Compression is used to subtly rub the track to make it more natural sounding and intelligible without adding distortion into a song that’s more “comfortable” and melodious to listen to. Compressors and limiters are used to reduce dynamic range i.e. the span between the softest and the loudest sounds of the track.
Using compression makes your tracks sound more polished by controlling maximum levels and maintaining the loudness of the track.
AUDIO COMPRESSION IN MODERN DAWS
Today, in most of the DAWs, there’s the ability to easily insert a compressor plugin to every single track in your track arrangement module. Refer to our DAW Buyer’s Guide to know more about choosing the right DAW for you.
In the older day, before digital DAWs, compressors were actual hardware modules. Since this hardware was limited in features, the audio engineers had to prioritize inserting the compressor to tracks that needed compression. Also, these types of compressors were time-consuming and may not provide the intended results.
AUDIO COMPRESSION EXPLAINED - HOW THE TOOL/PLUGIN WORKS?
Irrespective of the type of compressor you use – hardware unit or a plug-in, there are some parameters and controls that are common and are used in audio compression that you should be familiar with. Getting informed about these controls will enable you to work on a wide range of compressors.
The threshold control is the setting that fixes the level at which the compression effect is deployed. Only when the level passes above the threshold, it is compressed. For example, if the threshold level is set at -10 dB, only the signal peaks that extend above that level will be compressed.
It acts as an administrator over all the other controls and activates the compression.
The “knee” here refers to how the compressor passes between the non-compressed and compressed states of a signal that is running through it. Generally, compressors will offer one setting. But in some compressors, there is a switchable choice between both, a “soft knee” and a “hard knee” setting. Some compressors even allow you to control the selection of any position between the two types of knees.
These types of options in “knee” offer more space for the audio engineer to work out a suitable solution for the track.
Release time is the opposite of attack time. It is the time it takes for the signal to go from the compressed state back to the original non-compressed signal. Release times are considerably longer than attack times and generally range anywhere from 40-60 ms to 2-5 seconds. But it also depends on the type of compressor you use.
The release time should be set as short as possible without producing a “pumping” effect, which is generally the result of activation and deactivation of compression.
Compression ratio is the amount of attenuation applied to the signal. The higher the ratio settings are, the more you are compressing your track. By controlling the ratio, you determine how much compression is applied to the audio signal, once over the threshold level. There is a wide range of ratios available depending on the type and manufacturer of the compressor you are working with.
Since compressed signals are louder, compression-induced attenuation actually lowers the output. This is where the ‘Output gain’ or which is generally referred to as ‘make up gain’ comes in. The output gain is used to “make-up” for the attenuation done by the compressor. Hardware compressors achieve “make-up” gain using either tube or solid-state components which influences the amount of color or “effect” applied to your track.
WHEN & WHY IS COMPRESSION NEEDED?
Adding compression depends on the audio engineer’s mindset and demand of the track. It also depends on how the audio engineer wants to go with the audio track. As a thumb rule, compression is used on individual instruments and tracks.
As a thumb rule, compression is used on individual instruments and tracks.
The most basic use for a compressor involves taming transient material using downwards compression. Peak compression can be used to deal with transients that are overly present in the track. The compressor is used to reduce the level of transients while leaving sustained material unaffected.
Compression enables you to place similar elements within the same space of the track. Applying spatial effects like delay and reverb can help with creating space, but compression does a great job of tying grouped elements together as well.
Once you can pick out the compression sounds, you can tweak the ratio up and down. Make adjustments on the attack and release knobs, be it faster or slower. The latest DAWs provide a helpful indication of level meters as to understanding what is going on with the track, but as with all audio-related things, how it sounds is without a doubt the most crucial aspect.