Dynamic Processing

Dynamic processing involves the manipulation of an audio signal’s volume over time. This can be done through various effects and tools such as compressors, limiters, expanders, and gates, which are used for both corrective and creative purposes.

Compressors

Compressors essentially reduce the dynamic range of an audio signal, making softer sounds louder and loud sounds softer. This allows for more consistent volume levels and helps prevent clipping.
Key parameters to be aware of include threshold, ratio, attack, and release.
The threshold determines the level at which the compression begins, while the ratio sets how much compression is applied once the signal exceeds this threshold.
Attack and release control how quickly the compressor responds to and recovers from changes in the audio signal’s level.
Understanding how to manipulate these controls can dramatically affect the timing, tone and overall character of a mix.

Limiters

Limiters are a more extreme form of compression. They are used to prevent the audio signal from exceeding a certain level, thus avoiding distortion.
The main distinction between a limiter and a compressor is the high ratio used by the former, often ∞:1, effectively ensuring that the signal will not surpass the threshold.
Limiters are commonly used on the master bus during mixing and mastering to increase the overall level of a track while controlling peak level.

Expanders and Gates

Expanders and gates are the opposite of compressors. Instead of reducing the difference between quiet and loud sounds, they increase it.
Expanders work by decreasing the level of an audio signal once it falls below a set threshold. This helps to minimise noise during quiet sections.
Gates are a more extreme form of expansion. They mute the signal entirely once it dips below the threshold, useful for sudden and complete silence.
Gates are commonly used to eliminate leakage or bleed between multiple mics, for example, in a drum kit recording.

Side-chain Compression

Side-chain compression is a creative dynamic processing technique where the level of one audio signal is used to control the compressor on another audio signal.
Commonly used in many genres to create a ‘pumping’ effect, most recognisable in dance music where the kick drum causes other elements to ‘duck’ in volume.

By understanding these techniques and their parameters, you can not only fix problematic recordings but also creatively shape the sound and dynamics of your mixes. Familiarity with each process and its controls allows you to make informed decisions and produce high-quality, professional sounding music.