22
Testing FM Systems with FONIX 6500-CX Analyzers
Figure 1.3.8
Comparison of EHA90, the hearing aid response at 90 dB SPL, and
EFM 90, the FM response at 90 dB SPL
4.
To view both curves on the same screen requires the Multi-Curve Option:
a. Press
[MULTI].
b. Highlight
MULTIPLE
CURVES.
c. Press
[START].
d. If necessary, use [<, >] to display CRV 1 in the first slot. This curve is EFE90.
e. Use
[
∨
] to select the second slot.
f. If necessary, use[<, >] to display CRV 2 in the second slot. This curve is EHA90.
g. You may want to press [
∨
] and [FREEZE] to turn off the display of CRV 3, since
it is not relevant to this comparison. Similarly, press [
∨
] and [FREEZE] again to
turn off the display of CRV 4.
If you don’t have the Multi-Curve Option, press [CRT] to print out EFE90 and
compare it to EHA90.
5. If EFE90 is greater than 5 dB above EHA90, adjust the FM system 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.
See Figure 1.3.8.