Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors |
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Authors: | Sebastian Hoth |
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Institution: | (1) Univ.-HNO-Klinik Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany |
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Abstract: | Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with
Nucleus™ systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode,
the lower and upper limits of electric stimulus were defined by the values corresponding to “very soft” and “too loud”. Within
this dynamic range, the stimulus strength intervals associated to the verbal categories “soft”, “medium”, “loud” and “very
loud” were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments,
the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal
loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters
of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue
in favour of the development of flexible and channel-specific mapping function parameters in future CI systems.
Parts of this paper were presented at the 76th annual meeting of the Deutsche Gesellschaft für HNO-Heilkunde, Kopf- und Hals-Chirurgie
in Erfurt on 8 May 2005. |
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Keywords: | Cochlear implant Speech processor Loudness mapping Subjective scaling Fitting procedure |
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