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Abstract:
The speed of changes in speech production parameters was
investigated in four cochlear implant users, in response to
switching the speech processors of their implants on and off a
number of times in a single experimental session. The subjects
repeated short utterances many times in semi-random order. The
switches between hearing (on) and non-hearing (off) states were
introduced between utterances; the number of utterances between
switches was varied to minimize subject anticipation of the
switches. Using the times of on-off or off-on switches as line-up
points for averaging, the following parameters were compared
across the switches: median and symmetry of sibilant spectra, and
F1, F2, duration, and SPL of vowels. The speakers' vowel SPL and
duration had changed by the first utterance following the switch.
Changes in contrast between phonemes were less prevalent, but
just as immediate. The nature and speed of these changes indicate
that they are part of the same mechanism, one that attempts to
maintain clarity and intelligibility in the face of changing
acoustic transmission conditions.
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