Studio & Production

What do I need to know about compression?

Ratio: The degree of reduction of the dynamic range caused by the compressor. The ratio represents the difference between the audio signal increase coming into the compressor, and the increase at the output. As an example, a 5:1 ratio would mean that a 5dB increase in the audio signal coming into the compressor would result in a 1dB increase in the output.

Threshold: The level at which the compressor takes affect on the incoming audio signal. The compressor will have no effect on the signal below this level.

Knee: The precise point at which the compressor begins to reduce gain.

Hard Knee - the moment is sudden and definite

Soft Knee - a smooth transition from amplifier to compressor, allowing a wider range of threshold values to be effective.

Attack: The time the compressor takes before it affects the signal when it has breached threshold level. These settings are important in determining the final sound quality with respect to its brightness or high frequency content.

Fast attack - compresses the signal very quickly affecting the gain at waveform level.

Slow attack - allows the front, transient section of the sound to pass through the compressor before it begins having too large an affect.

Release: The time it takes the signal to return from a compressed one into a normal, amplified signal once the audio drops below threshold level.