2
Testing FM Systems with FONIX FP40 Analyzers
General Fitting Protocol
For the purposes of this workbook, we will assume that the hearing aid being tested has
been fitted appropriately for the client’s loss. We will adjust the FM system to the output of
the hearing aid.
Goals:
•
For students with mild to moderately-severe losses (<80 dB HL), the goal is to match the
output
of the hearing aid and the FM system when typical input signals are used. With
typical inputs, the FM output will be the same intensity as the hearing aid output.
•
For students with severe to profound losses (>80 dB HL), the goal is to match the gain of
the hearing aid and the FM system when typical input signals are used. With typical
input signals, the FM output will be about 10 dB more intense than the hearing aid out-
put.
Testing Order:
Start with 2-cc coupler tests and adjustments if possible. Follow up with real-ear verification.
If time doesn’t permit both test conditions, omit the 2-cc coupler tests. For both 2-cc coupler
and real-ear tests:
1.
Test the user’s hearing aid with typical input signal levels.
2. Test the FM system with typical input signal levels, and make any necessary adjust-
ments.
3.
Test the user’s hearing aid with high input signal levels.
4.
Test the FM system with high input signal levels, and make any necessary adjust-
ments.
Curve Labeling System
In order to efficiently record and refer to the various measurements, we have adopted a
curve labeling system created by Dr. Linda Thibodeau. This system is consistent with the
type of measurement made and the SPL of the test signal used.
•
The first letter indicates whether it was a coupler or a real-ear measurement.
– All coupler measurement labels begin with an “E” for “Electroacoustic.”
– All real-ear measurement labels begin with an “R” for “Real-Ear.”
•
The second and third letters indicate the type of test taken.
– “HA” means a hearing aid test
– “FM” means an FM-only test
– “FE” means an FM+ENV test with the signal delivered to the FM microphone
– “EF” means an FM+ENV test with the signal delivered to the environmental micro-
phone