1) Dilator 
• (n.) Anything which causes expansion esp. (Mech.) a tool for stretching open or expanding a tube, etc.
a non-linear device used for signal expansion
A device that causes expansion of the audio signal.
(ek-span´dәr) extender. plasma volume expander artificial plasma extender.
An amplifier whose gain is unity for signals below a specified threshold, then increases for higher input signal levels, or (b) is unity for signals above a designated threshold, then decreases for input signals below that threshold. Most professional units employ the second design. Noise gates are good examples of the lo-type expander. (WW)
A unit that increases the dynamic range of an audio signal. Works in reverse to a Compressor. 
Ex·pand'er noun Anything which causes expansion esp. (Mech.) a tool for stretching open or expanding a tube, etc. 
In audio engineering an expander is a form of automatic level control. By attenuating the signal below the threshold, the expander reduces low-level noise or expands the dynamic range of the recorded material.Expander is a cultivated variety of potato.
A type of dynamic range processor which reduces the gain of audio signals which are under an adjusta
a person or thing that expands. · a transducer that produces an output with a range of voltages greater than that of the input signal. Cf. compressor (def. 5).