Downward compression attenuates peaks above a threshold; upward compression raises quiet passages below one

There are two compression directions. Downward compression (the standard mode) attenuates signals above a threshold — it brings loud sounds closer to a ceiling. Upward compression raises signals below a threshold — it brings quiet sounds closer to a floor. Both reduce dynamic range but act on opposite ends of the amplitude range. A limiter is an extreme case of downward compression (infinite ratio). A noise gate is extreme downward expansion — it silences signals below a threshold. Parallel compression mixes a heavily compressed version with the uncompressed dry signal to preserve transient impact while adding density.

Examples

Vocalist with wide dynamics: downward compression at -12 dB tames peaks; upward compression below -24 dB raises quiet breaths. Parallel compression on drums: compressed signal adds sustain while dry path preserves the snare crack attack.

Assessment

A track has peaks at 0 dB and a noise floor at -40 dB. You want to raise the floor to -24 dB without touching the peaks. Which processor type and parameter settings achieve this?