How Audio Compression Works — A Guide for Producers and Engineers
Audio compression reduces the dynamic range of a signal by automatically attenuating audio that exceeds a defined threshold. It is one of the most-used tools in music production, mixing, and mastering.
The key parameters of a compressor are: threshold (the level at which gain reduction begins), ratio (how aggressively the signal above threshold is reduced), attack (how quickly the compressor responds to a peak crossing the threshold), release (how quickly the compressor stops attenuating after the signal drops back below the threshold), knee (how gradually the compression begins around the threshold), and makeup gain (added after compression to restore overall loudness).
A ratio of 2:1 means that for every 2 dB above threshold, only 1 dB passes through — a gentle setting. A ratio of 10:1 or higher approaches limiting, where the signal is nearly clamped to the threshold level.
Fast attack times (1–5 ms) clamp transients tightly, reducing punch and snap. Slow attack times (20–100 ms) allow the initial transient to pass through before compression engages, preserving punch. Release time affects how natural the compression sounds — too fast causes pumping; too slow causes the compressor to not fully recover between hits.
Compression ear training involves learning to hear the effect of threshold, ratio, attack, and release on audio — skills developed through games like SonicSandbox's Compressor game.