It took me a while to understand the fundamental concept of compression, but here’s my understanding of it in 200 words!
In presenting a song to an audience, we want to present the
- softest of the soft sounds without causing the ear to strain to listen
- loudest of the loud sounds without jarring the ear
Compression helps achieve these goals.
- Compression begins by identifying a volume level called the threshold.
- The compressor analyses the sound that passes through it. Sounds that are louder than the threshold are brought down in volume. (how much it is brought down is determined by a setting called the “ratio”)
- At this point, those part of the song that are below the threshold are unaffected, and those parts that are louder than the threshold are made softer (or compressed). The overall peak volume of the track is decreased as a result.
- Now using a control (called make-up gain) the overall volume of the signal is increased so that the peak volume is brought back to its original level. Note that the make-up gain affects all signals that pass through the compressor regardless of whether it is below or above the threshold.
- This results in
- the softer signals being increased in volume
- the peak volume being retained at its original level
- the difference in range between the softest and loudest signal is reduced
It helps in achieving the original two goals mentioned at the beginning of this post.
This, above, is the newbie take on what compression is.
There are some very good resources out there on the theory of compression which I have learnt from, Some that stand out are:
- The Ultimate Guide to Compression by Mixbus TV – The first couple of videos deal with the basic concepts of compression.
- Mixing with Mike: Power Compression – Michael White has some great videos on mixing in a series he calls Mixing with Mike. It covers a variety of subjects related to mixing. This series of 12 videos focusses on compression and the first 3 videos provide a gentle introduction to the subject.
Mixing from zero 