is used to expand the dynamic range of an audio signal. (They are basically the opposite of a compressor). An expander can also be considered an amplifier with two gain levels: the gain is unity for input signal levels above a certain threshold, and less than unity for signals with levels below the threshold. An expander boosts the high-level signals and attenuates low-level signals.
Thres Hold: Certain level for threshold, in db. Varies from -92 to 0.
Rate: Rate of mixing signals, in percent. Varies from 1 (minimal effect) to 100 (maximal effect).
RMS Time (1 to 5000ms): Time for root-mean-square calculation, in ms. Usually RMS Time is equal to 100 ms.
How to use
-Left-click-and-drag on the select a portion of the audio
-Click Effects menu and select Expander
Tip:
1. N db = 20 lg (Pn/P0)
N - number of db.
Pn - Level of sound pressure in pascals.
P0 = 2*105 pascals.
2. The expander is a type of dynamic processor. As the name implies, it increases the dynamic range of a signal such that low level signals are attenuated while the louder portions are neither attenuated or amplified.
3. This behavior is opposite to that of the Compressor.