Compression:
What is a compressor?
Well, compressor is basically an automated volume knob. This is a very important thing to know and remember as it sums up what a compressor is, and how it can be used in one simple metaphor. This, of course though, is very simplified. Compressors are actually a lot more complicated than this, but if you take it all in in little chunks, it can be easily manageable.
Threshold:
The threshold on a compressor is a level, measured in dB. And when the signal that you're compressing goes over that signal, it gets compressed, and if it doesn't, then no compression is being applied. For example, if you have the threshold set at -10dB, everything that goes over -10dB will be compressed, everything under it, won't. But the threshold is just a level, the actual compression is done by the ratio...
Ratio:
The ratio is where you actually decide how much compression is going to be applied, and the ratio is given in, well, a ratio. A compression ratio of 1:1 is no compression. What does the ratio actually mean I hear some of you ask? Well when the ratio is say, 2:1 every dB of signal over the threshold you denote makes it turn down by 2dB. So, a ratio of 3:1 means that for every dB over the threshold you give, it gets turned down by 3dB and this goes on until you get to around 30:1 or sometimes shown as infinity:1 which is when the signal is completely cutoff, this is known as limiting and is usually done by a specific plugin called (you guessed it) a limiter. But compression doesn't happen immediately, no no. Only if you want it to, anyway. There are two controls called the attack and release that control how fast or slow the compression happens...
Attack:
The attack is basically how fast the compression takes to happen, measured in ms. A long attack lets the original punch of the sound stay there, but the sound would have to be quieter than if it had a short attack and was more compressed.
Release:
The release on a compressor is how long the amount of compressed you specified earlier stay there, e.g a short release means the sound is only compressed for a short period of time, and a long release means the sound it compressed for a longer period of time. Hint: try to avoid having a short attack and release as this can cause weird clicks and artifacts.
Output Gain:
If you heavily compress the sound, it's going to be a lot quieter, so you use the output gain or output to get the sound back up to a normal listening level.
Understandably, this can go right over your head as it's just a bunch of letters, punctuation and symbols. So I decided to get you some pictures of audio files with different setting. All of these shown have a threshold of -20dB and a ratio of 4:1. (quite heavy compression settings.)
Uncompressed:
Audio: http://www.zshare.net/audio/74889208b83ec98f/
Compressed:
Audio: http://www.zshare.net/audio/7488938056497ae1/
It may look like that compressed one is just lot quieter, but because I compressed it, I'd be able to turn to turn it up so it would be louder.
Release of 500ms:
Audio: http://www.zshare.net/audio/74889451c81cc243/
As you can see, it's subtle but it's there, the audio file stay compressed for longer.
Attack of 30ms
Audio: http://www.zshare.net/audio/748895726e771702/
This one still retains the punch of the uncompressed, although the sound won't be able to be as loud as the compressed snare with no attack.
I hope you've all found this easy enough and enjoyable to read. If there are any problems, of I've gotten something wrong feel free to tell me. Also, if you have any questions on this topic, feel free to ask.
Peace!
-Kyle [Ekol]
