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Verifit User’s Guide Version 2.8
Page 42
8.5
ANSI 2003 Linear and AGC tests
FastFacts 8.5: ANSI 2003 Linear and AGC tests
1)
Press <Tests>, then highlight and <PICK> [Linear] or [AGC].
2)
Highlight and <PICK> [Start test]; test setup instructions will be displayed.
3)
Refer to
7.11: Coupling the hearing instrument
,
7.12: Positioning the hearing
instrument
and
2.6: Battery pill use and care
to prepare the instrument for
testing.
4) Turn the instrument ON
.
5)
Set the gain control (manual or programmable) to maximum with all other
controls set to provide the widest frequency response, greatest gain and
highest maximum output. AGC controls and/or programmable parameters
should be set to
minimize
AGC action (AGC off or threshold high, compression
ratio close to 1).
6)
Press <Continue> to run the test or press <Cancel> to abort the test. Note that,
if required, the Verifit will pause during the test to request that the gain control
be adjusted to the Reference Test Setting (RTS). If necessary, open the HIT
chamber and, without moving the hearing instrument, adjust the gain control
until the large vertical arrow on the screen prompt disappears. Press
<Continue> to resume the test.
During the AGC test, the Verifit will pause to request that AGC controls or
programmable parameters be set for
maximum
AGC effect. If the manufacturer
does not provide settings to produce maximum AGC effect, use settings that result
in the highest gain for soft sounds and the lowest gain for loud sounds. This will
typically result in the lowest compression threshold, a flat I/O curve and the
longest attack/release times. These are not “typical” characteristics but indicate
the adjustment range possible for these parameters.
If you are unsure which test sequence to run, try [AGC] first. If attack and release
times are all near zero, the instrument is probably linear.
