Coupler Measurements
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Chapter 3: Coupler Measurements
The Main Coupler Screen is the first operational screen you encounter when using the FP40. In it,
you can take coupler frequency response curves and view them in either dB GAIN or dB SPL. By
default, the FP40 comes with three different types of pure-tone sweeps that you can use as signals
to generate the response curves. You can also add the Composite and Digital Speech signals for test-
ing AGC and digital hearing aids.
3.1 The Main Coupler Screen
The display of the Main Coupler Screen varies depending upon whether you have chosen a pure-
tone source (available on all FP40 analyzers) or a Composite/Digital Speech source (optional).
3.1.1 Viewing a Pure-tone display
Figure 3.1.1—Pure-tone coupler screen
1. Display type: dB GAIN or dB SPL
2. Signal type
3. Pure-tone sweep type
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 used in graph
8. Battery current drain (only if turned on)
