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Testing FM Systems with FONIX 6500-CX Analyzers
2.3.8 Test FM system with high-level input—RFE90
1. Set up the FM system according to Section 2.1.2.
2.
Use [
∨
] to select CRV 2.
3. Use [>] to adjust the amplitude of CRV 2 to 90 dB SPL.
4. Press [START/STOP] to take measurement.
5. This curve will be referred to as RFE90 or the Real-Ear FM and Environmental
Response with 90 dB SPL input delivered to the FM microphone. See Figure 2.3.8.
6. If RFM90 is greater than 5 dB above RHA90, adjust the FM controls to obtain a better
match. As a last resort, adjust the settings on the hearing aid. If this must be done,
the teacher, parents, and therapists must be made aware that when the FM system is
used, the settings on the hearing aid must be changed for optimum performances.
For mild to moderate losses it is usually acceptable if the RFM90 is 5-10 dB below
RHA90.
Figure 2.3.8
Comparison of RHA90 (CRV 1) and RFE90 (CRV 2)
