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van der Beek/Briaire/Frijns
Audiol Neurotol 2015;20:1–16
DOI: 10.1159/000362779
10
ray) was given by the T-level of electrode 7, yielding the
following prediction formula:
T-level
(
electrode
) = 0.01 (
electrode
2
– 7
2
) +
0.025 (
electrode
– 7) +
T-level
electrode
7
(
in dB
).
(2)
As shown in figure 5b, the neighboring electrodes in the
center of the array provided comparable results, while the
mean r was reduced at both ends of the array (to r = 0.86).
R-values for electrodes 2, 5, 9 and 14 are not shown in
figure 5b, since these electrodes were active in only less
than 33% of the subjects (table 3).
The goodness of fit of equation 2 for the individual T-
levels was tested in the remaining 30% of the measured
data (fig. 5c; table 3a). Figure 5c shows scatter plots of the
predicted T-levels versus the measured T-levels for all 16
electrode contacts, while table 3a provides the associated
numerical data. Again, it is clear that the predictions are
slightly better for the center region of the array. This pro-
cedure was repeated with a number of other random se-
lections of 30% of the population, with essentially the
same result.
To obtain a T-level profile expressed in clinical units,
equation 2 can be reformulated as follows:
2 2
2 2
1 001
7 0025
20
7
02
7 05
7
7
-
10
10
.
lectrode
.
lectrode
lectrode
.
lectrode
.
lectrode
lectrode
T level lectrode
T-level
T-level
7
×
×
e
e
e
e
e
e
e
(in CU).
(3)
–18
El 13
El 14
El 15
El 16
El 9
El 10
El 11
El 12
El 5
El 6
El 7
El 8
El 1
El 2
El 3
El 4
–12 –6
–18 –12 –6
–18 –12 –6
–18 –12 –6
Predicted T-level (dB)
Measrued T-level (dB)
0
–6
–12
–18
–6
–12
–18
–6
–12
–18
–6
–12
–18
c
Fig. 5.
c
Scatter plot of the measured T-levels vs. predicted T-levels for the remaining 30% of the population for
each electrode.
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Fig. 5.
c Scatter plot of the measured T-levels vs. predicted T-levels for the remaining 30% of the population for each electrode.