Rapid changes in speech parameters with a change in auditory stimulation from a cochlear implant

Abstract

To investigate the speed of speech production changes in response to a change in hearing, the speech processors of two cochlear implant users were switched on and off a number of times in a single experimental session for each subject. The subjects repeated short utterances (‘‘a said,’’ ‘‘a shed,’’ ‘‘a sad,’’ and ‘‘a shad’’) many times in semi-random order. The transitions between hearing (on) and nonhearing (off) states were timed to occur between utterances, and the number of utterances between transitions was varied to minimize subject anticipation of the change. Using transition times as line-up points, values of median and skewness of sibilant spectra and vowel F1, F2, duration, and SPL were each averaged over repetitions of each utterance and compared across the on–off and off–on transitions. Vowel SPL and duration had changed by the first utterance following the transition, indicating that the subjects were using subtle aspects of the processor output to detect its state even in the absence of overt sound input. Changes in spectral median and skewness and F1 and F2 were less immediate, more varied, and differed between the two subjects. The paradigm is currently being refined to further investigate this issue. [Work supported by NIH.]