Audioscan Verifit - Manual (Page 106)

Verifit ® User's Guide Version 3.12  May 2015
sufficiently to raise them above threshold. In this case, the high frequency components may be shifted to a
lower frequency with a better hearing threshold where the available gain will render them audible.
Four modified versions of the Speech-std (1) test stimulus (Speech3150, Speech4000, Speech 5000 and
Speech6300) are provided in Speechmap to assist in verifying and adjusting frequency lowering devices. In
each of these modified test stimuli, the 1/3 octave band levels above 1000Hz are reduced by 30dB, except for an
isolated 1/3 octave band centered at the frequency indicated in the selected test stimulus’ name. With these
reduced band levels, the resulting LTASS produces a distinct 'cavity' between 1000Hz and the selected high
frequency band, as seen below for the FM Boom test signal. For clarity, the Speech3150 curve is not shown.
To test frequency-lowering:
1. From the Speechmap screen, choose either On-ear or Test box Mode. (Review 17.9: On-ear or Test box
mode.)
2. Program the hearing instrument so that the frequency-lowering feature is inactive.
3. Select Test 1 and choose 65dB from the level menu.
4. Choose Speech3150, Speech4000, Speech5000 or Speech6300 from the stimulus menu. Note that only the
LTASS is shown for these stimuli and targets (if selected) have been suppressed.
5. Press <Continue> to measure and store the long-term signal-averaged result. If the isolated band does not
appear in the Test 1 curve, it may indicate that the hearing aid has no gain at the selected band frequency.
This does not mean that the hearing aid will be unable to transpose the band to a lower frequency when
frequency lowering is enabled.
6. Program the hearing instrument to activate the frequency-lowering feature.
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