For every dB the sound goes above the threshold, how many dB should the compressor let through?
Let’s say you set up a compressor with a 2:1 ratio.
This means that for every 2 dB the sound goes above the threshold, the compressor will only let 1 dB through.
If the threshold is set at -10 dB and the sound jumps up to -8 dB (2 dB above the threshold), the compressor will only let 1 dB through and the sound will end up at -9 dB.
If the sound goes above the threshold by 4 dB, only 2 dB will be let through and the sound will end up at -8 dB.
ATTACK
Compressors need a certain amount of time (and they are also often supposed to do this) to bring the input value to the target value. This time is called 'attack time' or 'response time'.
The attack time is defined as the time between exceeding the threshold and reaching 63% of the setpoint.
RELEASE
There is a slow return process. This return process is usually much slower than the attack time. We speak of the release time. Practical values are in the range of 10 ms to 3 s.
A type of compression where the onset of compression is gradual. In normal or hard knee compression when the signal reaches the threshold the unit immediately begins to compress at whatever ratio is set.
