Expander
Definition
A dynamics processor that increases the dynamic range of a signal by attenuating levels that fall below a set threshold. The conceptual opposite of a compressor — where a compressor reduces peaks, an expander reduces the floor.
In Simple Terms
The opposite of a compressor — it makes quiet parts quieter. Useful for cleaning up background noise between notes or phrases without the abrupt on/off behavior of a noise gate.
In Practice
An expander set below the noise floor of a drum room microphone reduces low-level room noise between hits without the abrupt on/off behavior of a noise gate.
Common Confusion
An expander and a gate both reduce signal below a threshold, but a gate applies a near-total cutoff while an expander applies a gentler, ratio-based reduction. An expander sounds more natural in most cases.