Compression

• Refers to any process that is affected by, and controls, the level of volume.

• It’s essential when creating a balanced mix.

When every part can be heard throughout a mix at an appropriate level.

• Reduces the volume (dB) of an audio signal.

• This then means the signal has a more consistent dynamic range.

Difference in volume between the loudest and quietest part of an audio signal.

• Threshold.

• Ratio.

• Attack.

• Release.

• Make-up Gain.

• The level (dB) at which the compressor will start to turn down the input signal.

• Example: 0dB threshold would equal no compression, regardless of how loud the incoming signal is.

• This is the ratio at which the compressor will turn down the incoming signal.

• This is just a gain input to output ratio.

• Example: 4:1 ratio.

  • For every 4dB of input level, 1dB will be output.

  • With an input signal of 12dB at a 4:1 ratio, 3dB would be output.

• This is the speed at which the compressor will start to turn down a signal once it has passed the set threshold.

  • Fast attack: the compressor will clamp down quickly on the incoming signal, leading to more aggressive sounding compression.

  • Slow attack: the compressor will take longer to respond to turning down the incoming signal, leading to smoother and more natural sounding compression.

• This is the speed at which the compressor will start to let go of the incoming signal once it falls back below the threshold.

  • Fast release: the compressor will very quickly stop turning down the signal, only turning down the first part of the audio signal.

  • Slow release: the compressor will take longer to let go of an incoming signal, compressing it for longer and making the signal quieter overall.

• Turns up the compressed signal.

• This is important as compression will have made the overall signal quieter.

• Sometimes compression is used to just turn down the louder parts and it is not necessary to use make-up gain.

• Generally, you should only add the same amount of make-up gain that the compressor has turned down the signal.