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Section 1: Coupler Tests of FM Systems
6. Press [START/STOP] to begin a single frequency signal.
7. If necessary, use [<, >] to adjust the frequency to 1000 Hz.
8. Use
[
∨, ∧
] to adjust the signal level to 65 dB SPL.
9. Note the MIC OUT on the screen. This is the HEARING AID OUTPUT. See Figure
1.6.1.
10. Press [START/STOP] to turn off the signal.
1.6.2 Single frequency output of FM mic at 65 dB SPL
1. Set up the FM system for testing according to Section 1.4.2. The FM receiver should
be set to receive FM+ENV.
2. If you followed the procedure described in Section 1.6.1, you should be in Real Ear
Mode, with the analyzer ready to deliver a pure-tone signal of 1000 Hz at 65 dB SPL.
3. Press [START/STOP] to start the measurement.
4. Note the AID OUT on the screen. This is the FM OUTPUT.
5. Adjust the FM receiver volume so that the FM OUTPUT is matched to the HEAR-
ING AID OUTPUT found in Section 1.6.1. This matches the gain of the FM system
and the hearing aid.
6. Press [START/STOP] to turn off the signal.
1.6.3 Verify increase in signal level
1. Leave the FM system and the analyzer set up as described in Section 1.6.2.
2. Press [START/STOP] to start the single frequency measurement.
3. Press
[
∧
] repeatedly to increase the signal level to 80 dB SPL.
4. Note the AID OUT on the screen. This is the FM OUTPUT.
5. Compare the HEARING AID OUTPUT found in Section 1.6.1 to this new FM OUT-
PUT, and adjust the FM receiver volume control according to the following:
If the increase is:
• 10 dB, no further adjustments are necessary.
• 15 dB, reduce the FM receiver volume control so that the FM OUTPUT falls by 5
dB.
• 5 dB, increase the FM receiver volume control so that the FM OUTPUT increases
by 7 or 8 dB.
• 0 dB, the FM transmitter must have a very low compression threshold, so
increase the FM receiver volume control so that the FM OUTPUT increases by 5
dB.
