Compressors reduce the dynamic range of audio signals that exceed a user-selectable threshold by a specific amount. This is accomplished by reducing output levels as input levels increase above the threshold.
The amount of output level reduction that Impact applies as input levels increase is referred to as the
compression ratio. This parameter is adjustable in discrete increments. If you set the compression ratio to 2 (a ratio of 2:1), for each 2 dB that the signal exceeds the threshold, the output will increase only by 1 dB. With a setting of 4 (a ratio of 4:1), an 8 dB increase in input will produce only a 2 dB increase in output.