Setting the Compressor Threshold and Ratio
The most important Compressor parameters are Threshold and Ratio. The Threshold sets
the floor level in decibels. Signals that exceed this level are reduced by the amount set
as the Ratio.
The Ratio is a percentage of the overall level; the more the signal exceeds the threshold,
the more it is reduced. A ratio of 4:1 means that increasing the input by 4 dB results in
an increase of the output by 1 dB, if above the threshold.
As an example, with the Threshold set at −20 dB and the Ratio set to 4:1, a −16 dB peak
in the signal (4 dB louder than the threshold) is reduced by 3 dB, resulting in an output
level of −19 dB.