The Compressor effect reduces the difference between the loud and soft sections of the audio. This difference between loud and soft is often called "dynamic range". The effect is achieved by increasing the volume of the quieter sections of the audio. The terms of the compressor effect are as follows:
- Threshold is the volume level at which compression starts to be applied. The further right the slider, the louder the input has to be before compression is applied.
- Ratio - the further the slider is to right, the stronger is the compression applied.
- Attack time - the amount of time the compressor waits to respond after the Threshold is reached
- If the "Normalize to 0dB after compressing" box is checked, then after compression the audio will be amplified to the maximum amount possible possible without adding distortion. In Beta 1.3.x versions of Audacity, the user can choose a custom level to normalise to, e.g. to -3 dB which will make the loudest part of the audio 3 dB less than the maximum possible level without distortion.