36 FONIX FP40 Portable Hearing Aid Analyzer
3.1.2 Viewing a Composite display
Figure 3.1.2—Composite coupler screen
1. Display type: dB GAIN or dB SPL
2. Signal type
3. Composite weighting
4. Amount of noise reduction used (see Section 2.4.1.2)
5. Status of reference microphone
6. Leveling status
7. Source level of signal
8. RMS out measured by analyzer of current graph
9. Battery current drain (only if turned on)
3.2 Leveling
Leveling is the process by which the response of the sound chamber is measured and computer-cor-
rected so that a “flat” sound field is achieved. The leveling status can be saved into the FP40 analyz
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er’s permanent memory so you don’t have to level the analyzer every time you turn it on. However,
if you get your analyzer calibrated, or if you get a software upgrade, you should always level the
chamber again (and save the leveling).
If you are getting bad coupler frequency responses that you suspect are the fault of the analyzer
rather than the fault of the hearing aid, the first step of troubleshooting is to level the sound cham
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ber. Even if the screen says LEVELED, the response of the measurement microphone may have
