Common Compression Parameters
Threshold:
The threshold determines the level at which the compression begins to take effect. Any audio signal that exceeds the threshold will be subject to compression. For example, if the threshold is set to -20 dB, any signal above that level will be compressed, while signals below the threshold remain unaffected.
Ratio:
The ratio determines the amount of gain reduction applied to the audio signal once it exceeds the threshold. It expresses the relationship between the input level and the output level. For instance, a compression ratio of 4:1 means that for every 4 dB above the threshold, the output will only increase by 1 dB. Higher ratio settings result in more pronounced compression. Common ratio values range from 2:1 to 10:1 or even higher for heavy compression.
Attack Time:
The attack time controls how quickly the compressor responds once the audio signal crosses the threshold. It determines how fast the gain reduction is applied to the signal. A shorter attack time will result in a quicker reduction in level, capturing transients and shaping the initial portion of the sound. A longer attack time allows some of the transient to pass through uncompressed, which can help retain the natural dynamics of the audio.
Release Time:
The release time determines how long the compressor remains engaged after the audio signal drops below the threshold. It controls how quickly the gain reduction is reduced once the signal falls below the threshold. A shorter release time causes the compressor to disengage more rapidly, allowing the audio to return to its original dynamic range. A longer release time keeps the compressor engaged for a more extended period, resulting in a smoother and more consistent level.
Makeup Gain:
When applying compression, the overall level of the audio signal might decrease due to gain reduction. Makeup gain compensates for this reduction by increasing the overall output level. By adjusting the makeup gain, you can ensure that the compressed audio matches the original level or desired mix balance.
It's important to note that these parameters interact with each other, and finding the right settings requires careful listening and experimentation. Each audio source and musical context may require different compression settings to achieve the desired outcome.
By manipulating these common compression parameters, you can effectively control the dynamics of your audio, ensuring a more balanced and polished sound. In the next sections, we'll explore practical applications of compression in various scenarios, allowing you to apply these parameters in real-world situations.