Audioscan Verifit User Manual download pdf (Page 40)

Verifit

User's Guide Version 3.12



May 2015

3. Press <Continue> 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 <Setup>, then highlight and <PICK> [ANSI].

2. Highlight and <PICK> 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 <PICK> to select.

To change the frequencies for attack and release time measurements:

In the list of available frequencies, highlight and <PICK> the frequencies to be used to measure attack and

release time.

Press <Continue> 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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Audioscan Verifit User Manual Page 40