Target Coupler 169
those controls will have no effect on your custom target. To re-enable the target
controls, you must return to the Audiogram Entry screen and use the Generate
Target key (F3) to recreate an automatic target.
The NAL-NL1 targets in the Coupler Target screen have been slightly modified
from the original NAL-NL1 formula in order to better represent low gain pre-
scriptions. When the original NAL-NL1 formula calculates negative gain for a
coupler target, this gain is “clipped” to zero so that the final formula will never
prescribe negative gain for a patient. However, when measuring low gain hear-
ing aids, it is possible for a coupler measurement to show up as negative gain
while the corresponding real-ear measurement would show up as a slight posi-
tive gain. The FP35 instead clips the coupler gain at what would be the zero
gain of the real-ear insertion gain. This may produce some negative gain in the
Coupler Target screen. (The Coupler EarSim screen displays real-ear targets and
should not be affected.)
6.2 The Coupler Target and Coupler EarSim Displays
The Coupler Target screen converts the real-ear target into a coupler target and
displays it in either dB GAIN or dB SPL. The EarSim screen displays the real-ear
target in either dB insertion gain or dB SPL, converting any measurement taken
into simulated real-ear measurements.
Any measurement made in one of these screens will be automatically converted
into the other screen.
6.2.1 Viewing the Coupler Target Screen
The Coupler Target screen converts the real-ear target into a coupler target.
Coupler measurements can then be performed and compared directly to the
target. The only major difference between this screen and the basic Coupler
Multicurve screen (described in Chapter 3) is the addition of the coupler target.
To get the most accurate real-ear to coupler target conversions, measure the
patient’s unaided response in one of the real-ear measurement screens (Section
5.4.1) and the RECD in the Audiogram Entry screen (Section 5.3.6). When these
measurements are not taken, the FP35 substitutes average data. These averages
are sensitive to the selected age of the patient.
See Figure 6.2.1 for the following explanation of the dB GAIN display (the SPL
display is similar):
1. Type of display. This will be either dB SPL (coupler output) or dB Gain (cou-
pler gain).
2. Type of aid and the age of the patient.
3. Selected ear and leveling status of the sound chamber, including the real-ear
speaker angle that the coupler target is duplicating.
