Final answer:
The threshold in a compressor determines when the compressor starts reducing the dynamic range of the audio signal.
Step-by-step explanation:
The threshold in a compressor is the point at which the compressor starts to reduce the dynamic range of the audio signal. Essentially, it sets a level above which the compressor will begin to apply gain reduction. When the audio signal exceeds the threshold, the compressor reduces the level of the signal, effectively compressing the dynamic range of the audio.