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Verifit User’s Guide Version 2.8
Page 95
19.9 FM fitting and verification
FastFacts 19.9: FM fitting and verification
FM fitting is complex and strategies are varied and fluid. These instructions are
intended to provide the general principles involved, not a detailed and proven
method. They assume familiarity with the use of Speechmap in fitting hearing aids.
1)
Set up the hearing aid or receiver/earpiece as if to fit a hearing aid in REM or S-
REM mode. Set it for environmental microphone (EM) only operation. Set
Instrument
to [BTE] or [Body] to indicate the location of the EM.
2)
Follow
19: Speechmap Fitting Procedures
but in
19.7: Fitting to targets for mid-
level speech,
position LTASS 5 dB below the
+
targets (see note). Avoid
controls that change FM gain.
3)
Switch to FM only operation. If you are in S-REM mode, move the coupler and
hearing aid or earpiece outside the test chamber. In either REM or S-REM
mode, place the transmitter mic. close to the HIT reference mic. in the test
chamber. Turn the transmitter ON and close the test chamber.
4)
Change
Instrument
to [FM].
5)
Select an REAR test and, with [Stimulus]
at [Speech-shaped] and [Level] at [FM
Chest] or [FM Boom], adjust the receiver
and/or hearing aid to set the LTASS 5 dB
above
+
targets (see note). If possible,
use controls that don’t change EM gain.
If controls interact, you may need to repeat
these steps or change the order to reach an
optimum fitting.
NOTE:
If the FM system automatically reduces EM gain when FM is received (FM
priority), set the LTASS at the
+
targets in both EM and FM operation.
For procedures requiring a long coupler mic. cable see
2.4: Microphone connection
