Expansion

Role
Reduces amplification for very soft sounds which are not of interest to the wearer, such as very low level environmental sounds or noise generated internally by the hearing instrument.

End user benefit
Users, especially those with mild hearing loss, will be undisturbed by the noise of the hearing aid. The hearing instrument itself sounds quiet.

Our modern world is filled with many soft sounds that people with unimpaired hearing naturally filter out, for example the humming of a refrigerator or of a computer fan. Expansion reduces amplification of very soft sounds so that soft background noises and noise from the microphones are not distracting, providing the best backdrop for pleasurable listening and moving through rapidly changing sound environments without needing to make frequent manual adjustments.

EXPANSION SPECIFICATIONS
Setting	Maximum reduction	Threshold kneepoint (TK)
Low	3 (dB)	26 dB < TK < 38 dB TK ≈ 32 dB
Medium	6 (dB)	29 dB < TK < 41 dB TK ≈ 35 dB
High	9 (dB)	29 dB < TK < 41 dB TK ≈ 38 dB

RESOUND MODEL	CHOICE
LiNX Quattro 9 / LiNX Quattro 7 / LiNX Quattro 5/ LiNX 3D 9 / LiNX 3D 7 / LiNX 3D 5 / ENZO 3D 9 / Up Smart 9	Mild, Medium, Strong
ENZO 3D 7 / Up Smart 7 / Up 7	Mild, Medium
Enya 4, Enya 3, Enya 2 / ENZO 3D 5 / Magna 4, Magna 2 / Up Smart 5	Active*

*Active = Mild

The exact value of the kneepoint varies by model, as it is dependent on the components used in the device. It varies also from one frequency band to another.

Expansion ratio: 2:1
Attack time: 50 ms
Release time: 250 ms