How to Use Compression in Audio Recording

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By eHow Contributing Writer

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Compression in audio recording lessens the dynamic range of the audio by reducing the level of the louder parts. Compression is used in almost all commercial recordings and it is what gives many songs that "in your face" sound. The proper use of compression will let you bring out the quieter parts of your audio and make the entire piece sound louder.

Difficulty: Moderately Challenging

Instructions

Step 1

Set the threshold which sets the point at which the compressor will kick in and start reducing the audio level. The threshold works on decibel or dB units. Typically, zero dB is the highest setting, which would essentially not compress your audio unless it is clipping. The lower you set the threshold level will increase the how much compression occurs, so setting your threshold at -30dB will give you more compression that -15dB would.
Step 2

Adjust your ratio. The ratio determines how much the audio will be reduced when it exceeds the threshold. A ratio of 2:1 means that if your audio exceeds the threshold by 2dB it will be reduced by 1dB resulting in an output of 1dB over the threshold setting. A 4:1 setting will reduce the same 2dB over the threshold audio by 1.5dB resulting in an output level of .5dB over the threshold setting.
Step 3

Configure your attack and release settings. The attack setting will determine how long it takes the compressor to kick when audio goes over the threshold. This allows you to let the transient part of the sound to come through at the raw level before compression starts. The release time determines how long the compressor stays active once the audio goes below the threshold level. Attack and release can be tricky to get right, and many compressors have automatic attack and release options.
Step 4

Utilize your output gain or makeup gain to make your track louder. This will turn up the signal that is coming from the compressor. Use this instead of turning up the actual track input or output.
Step 5

Layer your compression gradually instead of using a lot of compression all at once. For instance, you may compress your kick drum but don't over do it because then you can compress your drums auxiliary bus and your overall mix, resulting in a more natural sound.
Step 6

Try some of these settings for different parts of your songs. Use a high threshold and a 2:1 ratio to get the pop-vocal sound for your vocals. This means that almost all of your vocal track will be compressed giving it that "in your face" sound. On bass guitar, set the threshold so that it is only compressing the loudest parts, then set a long attack and release time to give you a smooth bass sound.
Step 7

Tweak and experiment with the compressor. The best way to learn and get better at using the compressor is to experiment. Tweak your settings so that you get a sound you are happy with. Remember there are no rules in audio recording as long as it sounds good.

Comments

Chris916 said

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on 1/8/2009 Good advice, although every set of vocals requires its own different levels of compression. I just wish somebody gave us some examples of attack and release, but other than that this is a good article!