Ellen Stockmann

Effects of speaking condition and hearing status on vowel production in postlingually deaf adults with cochlear implant

This study investigates the effects of speaking condition and hearing status on vowel production by postlingually deafened adults. Thirteen cochlear implant users produced repetitions of nine American English vowels in three time samples (prior to implantation, one month, and one year after implantation); in three speaking conditions (clear, normal, and fast); and in two feedback conditions after implantation (implant processor turned on and off). Ten speakers with normal hearing were also recorded. Results show that vowel contrast, in the F1 versus F2 space, in mels, does not differ from the pre‐implant stage to the 1‐month stage. This finding indicates that shortly after implantation, speakers had not had enough experience with hearing from the implant to adequately retune their auditory feedback systems and use auditory feedback to improve feedforward commands. After 1 year of implant use, contrast distances had increased in both feedback conditions (processor on and off), indicating improvement in feedforward commands for phoneme production. Furthermore, after long‐term auditory deprivation, speakers were producing differences in contrast between clear and fast conditions in the range of those found for normal‐hearing speakers, leading to the inference that maintenance of these distinctions is not affected by hearing status. [Research supported by NIDCD.]

The effect of masking noise on acoustic‐phonetic contrasts in post‐lingually deafened cochlear implant users

This study examined the effect on the vowel contrast distance (average inter‐vowel distance in the F1−F2 plane) of gradually decreasing the signal‐to‐noise ratio (SNR) in the auditory feedback of a post‐lingually deafened cochlear implant (CI) user at 1‐month and 1‐year following CI processor activation. Masking noise, mixed with normal levels of speech feedback, was presented through the headpiece of a research sound processor to the CI user. As a control, an analogous procedure was used for a normal‐hearing speaker where the masking noise and speech feedback were delivered over headphones. The SNR was gradually decreased over seven steps as the speakers produced ten repetitions of two vowel contrasts (ae\/[g\/] and i\/u). Speech SPL and vowel contrast distance were measured at all seven masking noise levels. Data from both subjects showed that SPL gradually increased with decreased SNR, while contrast distance decreased. The effect was greater after 1 year of experience with a CI than at 1 month. The eff...

Language‐specific, hearing‐related changes in vowel spaces: A study of English‐ and Spanish‐speaking cochlear implant users

This study investigates the role of hearing in vowel productions of postlingually deafened cochlear implant (CI) users. Based on the hypothesis that competing demands of intelligibility and economy of effort influence vowel production, we predicted that speakers of a language with a more crowded vowel space, such as American English, would show an increase in average vowel spacing (AVS the average inter‐vowel distance in the F1‐F2 plane) with the provision of hearing from a CI; whereas speakers of a language with fewer vowels, such as Spanish, would not. Results of a preliminary on–off study supported the hypothesis: with hearing from a CI, 7 English‐speaking CI users all increased AVS; however, among 7 Spanish speakers, some increased AVS and some reduced it. The current study is exploring these findings further with new groups of CI users and normal‐hearing speakers of English and Spanish and an elaborated paradigm that includes different speaking rates and comparisons between pre‐implant and post‐impla...

Effects of hearing status and perturbation with a bite block on vowel production

This study explores the effect of hearing status on adaptation to a bite block in vowel productions of normal hearing (NH) adults and adults who use cochlear implants (CI). CI speakers are tested prior to and following experience with the implant. Different sized bite blocks (BB) are used to create unusual degrees of mandibular opening for vowel productions in an /hVd/ context (had, head, heed, hid, and hod). Four conditions are elicited from each NH and CI speaker: (1) no BB with hearing (CI processor on), (2) no BB with no hearing (NH speakers with masking noise and CI speakers with processor off), (3) BB with no hearing, and (4) BB with hearing. Prior to fitting with the implant, CI speakers are tested without hearing in two conditions: (1) no BB and (2) BB. Spectra of the vowel productions are analyzed for dispersion of tokens in the F1–F2 plane in the four conditions. Pilot results support the hypothesis that prior to fitting, CI users are less able to adapt to perturbations than NH speakers and that...

Audio‐visual integration in listeners with normal hearing and hearing aid users

In listeners with normal hearing, the sight of a speaker’s face articulating a syllable can influence the auditory percept, most observably when the auditory and visual stimuli are different from one another. This study investigates differences in audio‐visual (AV) integration (‘‘the McGurk effect’’) between adults with hearing loss who wear hearing aids (HA) and their normal‐hearing (NH) counterparts. The following hypothesis is being tested: HA users will rely more on visual input and thus be biased more toward the visual stimulus in the mismatch condition. Audio‐visual stimuli from three speakers are presented, pairing the consonants /b/, /d/, and /g/ with the vowels /a/, /i/, and /u/, in three conditions (auditory‐only, visual‐only, and AV) to the two subject groups, NH and HA. Participants label each stimulus according to the consonant perceived. Responses are coded into four categories: fusion, combination, auditory, or visual. Data analysis examines the relative strength of visual influences in the...

Efficacy of proprioception in achieving vowel targets when acoustic feedback is blocked: An EMMA study of production under contrasting noise conditions

In a magnetometer study of six normal hearing native English speakers producing vowels in an /hVd/ context, masking noise was used to interfere with acoustic self‐monitoring of speech production. Data were obtained under two conditions. In the first, subjects received unmodified audio through earphones. In the second condition audio feedback was replaced by white noise at 95 dB SPL. Under both conditions subjects were instructed to use a real time SPL display for regulating loudness to avoid Lombard effects. Midsagittal transducer data, corrected for head movement, were obtained for the lower incisors, lips, and three points on the tongue. A consistent measurement point was obtained by first delimiting each vowel using RMS thresholding of the acoustics, then selecting the 1/3 offset between those limits. Results showed, contrary to expectation, that neither formants nor the measured articulator locations under the noise condition were more dispersed than when acoustic feedback was available; for some subj...