Expander

Adds expander effect to the audio data array. The expander is essentially an amplifier with a variable gain control.

Parameter	Description
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	Time for root-mean-square calculation, in ms. Usually RMS Time is equal to 100 ms.

Tip:

See also: Apply a Special Effect or Filter
N db = 20 lg (Pn/P0)

N - number of db.
Pn - Level of sound pressure in pascals.
P0 = 2*105 pascals.
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.
This behavior is opposite to that of the Compressor.