Audioscan Verifit - Manual (Page 40)

Verifit ® User's Guide Version 3.12  May 2015
3. Press to exit
ANSI test frequencies
The Frequencies feature allows hearing instruments to be evaluated at the Special Purpose Average (SPA)
frequencies defined by ANSI S3.22, rather than the default High Frequency Average (HFA) frequencies. The
choice of SPA (or HFA) frequencies influences the average OSPL90, average full-on gain, reference test gain,
bandwidth and equivalent input noise. The frequencies at which distortion is measured are one-half the selected
SPA frequencies. You can also select the frequencies at which attack and release times are measured.
To change the averaging frequencies:
1. Press , then highlight and [ANSI].
2. Highlight and the HFA/SPA button to generate a drop-down list box of alternate test frequencies.
3. Highlight the desired HFA/SPA test frequencies and press to select.
To change the frequencies for attack and release time measurements:
In the list of available frequencies, highlight and the frequencies to be used to measure attack and
release time.
Press to exit.
Test box calibration facts
Test box microphone calibration establishes a correction curve for the uncalibrated test box reference
microphone by comparison with the factory calibrated coupler microphone. It may be performed as often as
desired but will be invalidated at 12 am the following day or at 12 am the following Monday, depending on the
choice of Daily or Weekly calibration interval. After the calibration has expired, the message window will turn
blue and you will be prompted to calibrate whenever you attempt a test that uses the test box microphones.
Your calibration curve should be similar to the one shown but may be at a different level. It should remain stable
over time. Irregularities in the calibration curve may be the result of not properly aligning the microphones. See
Calibrating test box reference microphone.
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