Frye FONIX 7000, Руководство оператора

Страница: 43 / 216

General Operation
35
HFA (High Frequency Average) 1000, 1600, 2500
SPA (Special Purpose Average) 800, 1250, 2000
SPA 1250, 2000, 3150
SPA 1600, 2500, 4000
SPA 2000, 3150, 5000
IEC–(HAIC) 500, 1000, 2000
2.3.1.2 Noise reduction
Noise reduction is used in noisy testing environments. Pure-tone noise reduc-
tion takes several measurements at each frequency and averages those measure-
ments together. Larger noise reduction numbers lead to smoother curves but
increase the amount of time it takes to complete a pure-tone sweep.
For example, if you select “4” as the pure-tone noise reduction setting, 172 mea-
surements (43 x 4) will be taken with every normal pure-tone sweep.
2.3.1.3 Delay times
The 7000 test system allows you to refine your pure-tone measurements with
many different adjustments for delay times. This choice is allowed because
some hearing aid circuits take a longer time than others to adjust to changes in
amplitude or frequency. If the measurement is made too quickly, an artifact in
testing will be created. If the measurement takes too long, the test is longer than
necessary.
In determining the length of time needed for a proper measurement, a good rule
is to use twice the published attack time of the hearing aid. If you are unsure
of the attack time, you can experiment with longer times and shorter times and
see if there is any difference in the test results. Linear aids can be tested very
quickly, so a delay of 20 msec is usually fine. Other aids are quite variable. See
Section 2.3.1.1 for a description of the available delay settings.
The 7000 test system has standard delay times that are determined by the aid
type selection. When you set the delay settings to Default, the following delay
times will be used:
Measurement Standard AGC Adaptive
SWEEP START 100 ms 500 ms 2000 ms
SWEEP MEAS 20 ms 50 ms 100 ms
MISC START 100 ms 500 ms 2000 ms
MISC MEAS 20 ms 100 ms 200 ms
I/O START 100 ms 500 ms 2000 ms
I/O MEAS 20 ms 100 ms 200 ms