What Is An Audio Compressor?

An Audio Compressor is an audio signal processor providing automatic volume control. It makes the Output signal level more balanced by reducing the level differences in the Input signal. It reduces the level difference between Input and Output with the parameters you specify. I will explain these parameters later.

We can think of the compressor as an Audio Engineer who makes Fader Automation according to changes in volume level. An engineer who reduces the sound level when it exceeds the specified level (threshold) and does not intervene when it falls below the specified level.

Let's take a look at the parameters of the compressor Threshold: The threshold determines the signal level at which the compressor will begin to interfere. For example, when we set the Threshold on the Compressor as -10 dB, the compressor will not be activated for the signal below this level; The compressor will be activated only when the signal level exceeds -10 dB.

Ratio: Controls how much the output signal is attenuated relative to the input signal in dB after the threshold is exceeded.

• If the ratio is 1:1, there is no compression at all.

• If the ratio is set at 2:1, for every 2 dB of sound that goes over the threshold, you get 1 dB of output above the threshold. So if the signal goes over the threshold by 10 dB, the compressor reduces this signal so it’s now 5 dB over the threshold.

• If the ratio goes up to 8:1, for every 8 dB of sound over the threshold you would get 1dB of output above the threshold. So if the signal goes over the threshold by 16 dB, the compressor reduces this so only 2 dB goes over the threshold.

Attack: Response time is in Milliseconds (ms). Determines how many milliseconds the compressor will activate after the signal level exceeds the threshold.

Release: Like the attack parameter, the response time is in milliseconds. It determines how long it takes for the compressor to return to normal level when the signal level falls below the threshold.

Knee: Determines how the compressor will act at the threshold level. The knee can be thought of as a characteristic of the compressor rather than a control or a parameter.

The knee can be divided into two general categories: Soft and Hard.

• Soft knee features, compression starts below the threshold level and as the level increases, compression also increases. In this way, the compressor is activated smoothly.

• Hard knee features, when the signal exceeds the threshold level, it is activated suddenly with the settings on the compressor.

Output/Make-Up Gain: Expressed in dB. When the compressor operates at low threshold levels and high ratio, the output signal drops significantly. To compensate for this, an amplifier is installed in the compressor, which increases the signal level and output of this compressor.

Gain Reduction Meter: This shows how much dB reduction the compressor applies. This is great for checking that your threshold, ratio, attack, and release settings are resulting in the kind of compression that you would like. Having this visual insight is useful for fine-tuning these settings.