Audioscan Verifit - Manual (Page 52)

Verifit ® User's Guide Version 3.12  May 2015
10 Other Test Box Measures
In addition to the tests of ANSI S3.22, the Verifit also provides the following tests in the test box:
Manual control: Coupler and test box reference mic. SPL and coupler mic. distortion at selected 1/12th octave
frequencies and stimulus SPL of 0 and 40 – 90 dB in 5 dB steps. Can be used as a dual channel sound level
meter with 1/12th octave, A and C filters.
Feedback Reduction: This test is a before and after comparison of curves with the hearing instrument feedback
reduction deactivated vs. activated.
Directional: A real time assessment of directional performance by analyzing the response to the left and right
speakers.
Distortion: Harmonic distortion at 2nd or 3rd harmonics and 2nd plus 3rd with input levels varying from 60 –
90 dB SPL.
Multicurve: 1 – 4 curves of coupler SPL or coupler gain for swept tones or pink noise in 1/12th octaves at
selected input SPL of 0 or 40 to 90 dB in 5 dB steps. Can be used as a 1/12th octave spectrum analyzer by
setting stimulus to 0 dB.
Battery drain: A 10 second test of battery current drain with no acoustic input, a 1 kHz 65 dB input SPL, and
an average for 90 dB input SPL at the HFA or SPA frequencies selected in Setup.
Harmonic distortion
This test measures harmonic distortion at 2nd or 3rd harmonics with input levels varying from 60 – 90 dB SPL.
It also presents the sum of 2nd and 3rd harmonics as total harmonic distortion (THD). For hearing aids, this
differs little from true THD.
1. Press <Tests>, then highlight and <PICK> [Test box measures], then highlight and pick [Distortion].
2. Refer to Coupling the hearing instrument, Positioning the hearing instrument and Battery pill use and care to
prepare the instrument.
3. Turn the hearing instrument ON.
4. Highlight and <PICK> [Start test].
5. Highlight and <PICK> [Harmonics], then highlight and <PICK> THD, 2nd or 3rd from the drop-down list.
6. Highlight and <PICK> [Input], then highlight and <PICK> the desired input level (60 – 90 dB SPL) from the
drop-down list.
7. Press <Continue> to run the test. Distortion will be displayed at 1/3 octaves in graphic and in tabular form.
Noise reduction
This test captures a response curve before the hearing instrument reacts to the presence of noise; a comparison
curve shows the hearing instrument reacting in real-time. The thick curve is the output before the noise
reduction is activated and the thin line is the output as the noise reduction takes effect. The test also provides an
overall rms noise reduction value in dB.
1. Press <Tests>, then highlight and <PICK> [Test box measures], then highlight and pick [Noise reduction].
2. Highlight and <PICK> Test 1, 2 or 3.
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