148 FONIX FP35 Hearing Aid Analyzer
5. Press [F2] to select AIDED 1. Make sure COMP is the selected source type
above F4, and the SOURCE is OFF. Use [F4] and [
∨] to make these selec-
tions, if necessary.
6. Press [START/STOP] to start a second measurement.
7. Ask your patient to sustain an “eee” sound again. Press [START/STOP] dur-
ing the vocalization when the measurement has stabilized. (You can then
tell your patient to stop.)
8. Compare AIDED 1 to the “UNAIDED” measurement to see how your vent
adjustments have changed the response of the hearing aid.
9. Press [NEXT] to view the Insertion Gain screen. This will show you the
actual difference that your adjustments made—the first measurement is sub-
tracted from the second measurement.
5.7 Miscellaneous Real-Ear Measurements
The measurements and information described in this section can be performed
in the SPL screen, the Unaided and Aided screen, and the Insertion Gain screen.
5.7.1 Measuring a Single Frequency Response
It is sometimes useful to be able to determine the response of the hearing aid to
a single frequency and how that response changes as the frequency and ampli-
tude of the signal changes.
The USER LEVEL must be set to ADVANCED in the Default Settings menu. See
Section 2.3.2 for details.
To measure the single frequency response:
1. Hold down the [F4] key for half a second in any of the real-ear measurement
screen.
2. Use the [
∨, ∧] keys to select SINGLE.
3. Press [START/STOP] to make the selection.
4. Press [START/STOP] again to start the single frequency signal. It will be a
pure-tone warble.
5. Use [<, >] to change the frequency of the pure-tone warble.
6. Use [
∨, ∧] to change the amplitude of the pure-tone warble.
See Section 2.5.1.4 for information about changing the warble rate (or turning
off the warble) of the pure-tone signal.
5.7.2 Measuring Harmonic Distortion
Harmonic distortion is when the hearing aid returns energy at frequencies not
present in the source signal. The FP35 allows you test for this phenomenon very
easily. See Section 2.5.1.2 for more information on the harmonic distortion mea-
surement.
