Threshold
The level where a compressor, limiter, or gate wakes up and starts changing the signal.
See it
What it is
A threshold is the level that tells a dynamics processor when to act. A compressor or limiter reduces signal that rises above its threshold; a noise gate usually attenuates signal that falls below its threshold. On a digital plugin the value is normally shown in dBFS.
Set it from the material, not from a memorized number. For spoken-word compression, lower the threshold until loud phrases show roughly 3 to 6 dB of gain reduction while ordinary speech stays natural. For a gate, start just above the measured noise floor so room hiss closes the gate but quiet words still open it.
Gotcha: the threshold says when, not how much. Ratio, knee, attack, and release decide what happens after the crossing. Input gain also changes how often the signal crosses the line, so a threshold copied from another track is meaningless when that track was recorded at a different level. Some classic hardware does not even offer the control: the UREI 1176 has a fixed internal threshold, and you set the amount of compression by driving its Input knob harder.
Ask AI for it
In REAPER's ReaComp, set a 3:1 ratio, 10 ms attack, and 100 ms release, then lower the Threshold until the loudest voiceover phrases produce 3 to 6 dB of gain reduction. Leave Auto make-up off while setting the threshold, confirm quiet phrases are not being clamped, and report the final threshold in dBFS.