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Section 1: Coupler Tests of FM Systems
6. Use [>] to select a source level of 90 dB SPL.
7.
Press [START/STOP] to begin the sweep.
8.
This response will be referred to as the Electroacoustic Hearing Aid Saturation
Response or EHA90. See Figure 1.5.3.
1.5.4 Test FM system with high-level input — EFM90
1. Set up the FM system for testing according to the FM setup described in Section
1.4.2.
2.
Use [
∨
] to select CRV 2.
3. Use [>] to select a source level of 90 dB SPL.
4.
Press [START/STOP] to make the measurement.
5. CRV 2 is now the Electroacoustic FM Saturation Response or EFM90.
6.
Compare EHA90 (CRV 1) to EFM90 (CRV 2). If EFM90 is greater than 5 dB above or
10 dB below EHA90, adjust the maximum output control if possible on the FM
receiver or on the hearing aid if necessary. If the hearing aid is adjusted, 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 may be acceptable if the EFM90 is 5-10 dB below EHA90. See
Figure 1.5.4.
Figure 1.5.4
Comparison of EHA90 (CRV1), the hearing aid response at 90 dB
SPL with EFM90 (CRV2), the FM response at 90 dB SPL