Appendix E
189
Fitting Formula Tables
The conversions used by the FONIX 7000 Test System to convert
audiograms to target gain curves are the following:
NAL-RP FITTING FORMULA CALCULATION
The insertion gains at each frequency are calculated according to
the following formulas:
Freq (Hz)
Insertion Gain (dB)
250
X + .31 HTL - 17dB + S
500
X + .31 HTL - 8dB + S
750
X + .31 HTL - 3dB + S
1000
X + .31 HTL + 1dB + S
1500
X + .31 HTL + 1dB + S
2000
X + .31 HTL - 1dB + S
3000
X + .31 HTL - 2dB + S
4000
X + .31 HTL - 2dB + S
6000
X + .31 HTL - 2dB + S
8000
X + .31 HTL - 2dB + S
Where you calculate X and S (Slope correction values) as follows:
a. T = (HTL @ 500Hz) + (HTL @ 1000Hz) + (HTL @ 2000Hz)
b. If T is less than or equal to 180dB, then
X = .05 x T
If T is greater than 180dB, then
X = (.05 x 180dB) + (.116 x ( T - 180dB)
c. If the HTL at 2000 Hz is less than 95dB, S = 0
If the HTL at 2000 Hz is greater than or equal to 95dB, then
apply the following slope correction factors at each frequency
based on the 2000Hz measurement:
2000Hz
250 500 750 1000 1500 2k 3k 4k 6k 8k
HTL (dB)
95
4
3
1
0
-1
-2
-2 -2
-2 -2
100
6
4
2
0
-2 -3
-3 -3
-3 -3
105
8
5
2
0
-3
-5
-5 -5
-5 -5
110
11
7
3
0
-3
-6
-6 -6
-6 -6
115
13
8
4
0
-4
-8
-8 -8
-8 -8
120
15
9
4
0
-5
-9
-9 -9
-9 -9
Содержание FONIX 7000
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Страница 189: ...Calibration 181 Figre B 2 Calibrating the insert earphone ...
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