Real-Ear Measurements 149
The USER LEVEL must be set to ADVANCED in the Default Settings menu. See
Section 2.3.2 for details.
1. Press [MENU] from any real-ear measurement screen.
2. Press [NEXT] to enter the Custom menu.
3. Select DISTORTION using the [
∨, ∧] keys.
4. Select the distortion type desired by using the [<, >]keys. See below for
definitions of distortion types.
5. Press [EXIT].
6. Press [F4] to select NORM.
7. Press [START/STOP] to run normal frequency sweep.
Figure 5.7.2—Measuring harmonic distortion
After running a normal sweep, the graph will have bars depicting the percentage
level of harmonic distortion at different frequencies. The scale for the harmonic
distortion measurements is given on the right vertical axis of the graph.
In the past, FONIX analyzers have not measured harmonic distortion when the
signal level was set to 90 dB SPL or higher. This is called the “90 dB harmonic
distortion rule.” Since hearing aids in recent years have become more sophis-
ticated and able to handle loud signals, we have turned this off this rule by
default. However, if you would like to use it, go into the Custom Menu (press
[MENU], [NEXT], [NEXT]) and turn ON the DIST 90 dB RULE..
