The effect of parametric variations of cochlear implant processors on speech understanding

Philipos C. Loizou, Oguz Poroy, Michael Dorman

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

This study investigated the effect of five speech processing parameters, currently employed in cochlear implant processors, on speech understanding. Experiment 1 examined speech recognition as a function of stimulation rate in six Med-E1/CIS-Link cochlear implant listeners. Results showed that higher stimulation rates (2100 pulses/s) produced a significantly higher performance on word and consonant recognition than lower stimulation rates (<800 pulses/s). The effect of stimulation rate on consonant recognition was highly dependent on the vowel context. The largest benefit was noted for consonants in the /uCu/ and /iCi/ contexts, while the smallest benefit was noted for consonants in the /aCa/context. This finding suggests that the /aCa/consonant test, which is widely used today, is not sensitive enough to parametric variations of implant processors. Experiment 2 examined vowel and consonant recognition as a function of pulse width for low-rate (400 and 800 pps) implementations of the CIS strategy. For the 400-pps condition, wider pulse widths (208 μs/phase) produced significantly higher performance on consonant recognition than shorter pulse widths (40 μs/phase). Experiments 3-5 examined vowel and consonant recognition as a function of the filter overlap in the analysis filters, shape of the amplitude mapping function, and signal bandwidth. Results showed that the amount of filter overlap (ranging from -20 to -60 dB/oct) and the signal bandwidth (ranging from 6.7 to 9.9 kHz) had no effect on phoneme recognition. The shape of the amplitude mapping functions (ranging from strongly compressive to weakly compressive) had only a minor effect on performance, with the lowest performance obtained for nearly linear mapping functions. Of the five speech processing parameters examined in this study, the pulse rate and the pulse width had the largest (positive) effect on speech recognition. For a fixed pulse width, higher rates (2100 pps) of stimulation provided a significantly better performance on word recognition than lower rates (<800 pps) of stimulation. High performance was also achieved by jointly varying the pulse rate and pulse width. The above results indicate that audiologists can optimize the implant listener's performance either by increasing the pulse rate or by jointly varying the pulse rate and pulse width. (C) 2000 Acoustical Society of America.

Original languageEnglish (US)
Pages (from-to)790-802
Number of pages13
JournalJournal of the Acoustical Society of America
Volume108
Issue number2
DOIs
StatePublished - 2000

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central processing units
pulse rate
stimulation
pulse duration
vowels
Commonwealth of Independent States
speech recognition
filters
bandwidth
phonemes
Pulse
Cochlear Implant
Consonant
Stimulation
pulses

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

Cite this

The effect of parametric variations of cochlear implant processors on speech understanding. / Loizou, Philipos C.; Poroy, Oguz; Dorman, Michael.

In: Journal of the Acoustical Society of America, Vol. 108, No. 2, 2000, p. 790-802.

Research output: Contribution to journalArticle

Loizou, Philipos C. ; Poroy, Oguz ; Dorman, Michael. / The effect of parametric variations of cochlear implant processors on speech understanding. In: Journal of the Acoustical Society of America. 2000 ; Vol. 108, No. 2. pp. 790-802.
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