Audioscan Verifit - Manual (Page 93)

Verifit ® User's Guide Version 3.12  May 2015
are of little value in estimating amplified speech levels. Matching amplified speech to the LTASS targets at
levels from 50 to 75 dB SPL provides much better assurance that fitting goals are being met.
4. There is no requirement to input client gender. The impact of gender on REAR targets is less than +/- 1dB.
5. There is no requirement to input hearing aid experience. An "Experienced" user is assumed. The reduction in
NAL-NL2 REAR targets for an inexperienced user is less than 4.5 dB.
6. There is no provision to generate targets for tonal languages. The REAR targets for tonal language differ less
than 2.5 dB from those for non-tonal languages.
7. There is no requirement to input the number of compression channels. This may be useful when the signal
used for verification is not the signal for which the targets were developed. It is irrelevant when using real-
speech signals to match speech targets and when using narrow-band signals to match narrow-band maximum
output targets.
8. There is no requirement to input compression speed. It has no impact on REAR targets.
9. There is no requirement to input earmold tubing type. It has no impact on REAR targets.
10. There is no requirement to input vent size or fitting depth. They have no impact on REAR targets.
11. For sound-field threshold the speaker is assumed to be at 45 degrees. For on-ear measurements, the speaker
is assumed to be at 0 degrees and the reference microphone is assumed to be on the head surface.
12. The SII calculation is per ANSI S3.5-1997 and is the same for all fitting methods.
Camfit in Speechmap
Camfit is an approach to fitting hearing aids developed by Brian Moore at the University of Cambridge, UK. It
specifies the level-dependent gain required to correct abnormal loudness as modelled by his cochlear hearing
loss simulation. It provides two approaches to correcting for the hearing loss:
Camfit restoration aims to amplify sounds that are soft, comfortable and loud for a person with normal hearing
so that they are soft, comfortable and loud for a hearing aid wearer. This is the stated goal of the IHAFF
(International Hearing Aid Fitting Forum) fitting method.
Camfit equalisation aims to amplify speech to produce the same loudness in each critical band. It has been
argued that this is likely to give the highest intelligibility for a given overall loudness. This is the rationale
behind the NAL fitting methods and will generally produce similar targets.
Using Speechmap
The Speechmap fitting environment provides a number of distinctly different stimuli. Speech and noise are
analyzed in 1/3 octave bands and for most speech stimuli data are presented as 3 curves. The top curve is the
level exceeded 1% of the time (speech peaks), the lower curve is the level exceeded 70% of the time (speech
valleys) and the middle curve is the average. Starting a test causes the signal to be presented continuously - the
speech signals run in a loop - and the curves are updated frequently to show any changes you make to the
hearing instrument. Pressing <Continue> restarts the speech passage and the curves are then calculated for the
entire passage, producing an accurate display of the speech region and LTASS, and an accurate SII calculation.
When using live speech, a <Freeze curve> button captures short-term speech features. See SII calculation in
Speechmap and Speechmap Technical Details.
Before starting, please see On-Ear Measures - Setup, Speechmap Setup, Speechmap facts, On-ear or Test box
mode.
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