Changes in speech intelligibility of postlingually deaf adults after cochlear implantation

The Impact of Bimodal Hearing on Speech Acoustics of Vowel Production in Adult Cochlear Implant Users

PURPOSE

This study aimed to investigate the acoustic changes in vowel production with different forms of auditory feedback via cochlear implant (CI), hearing aid (HA), and bimodal hearing (CI + HA).

METHOD

Ten post-lingually deaf adult bimodal CI users (aged 50-78 years) produced English vowels /i/, /ɛ/, /æ/, /ɑ/, /ʊ/, and /u/ in the context of /hVd/ during short-term use of no device (ND), HA, CI, and CI + HA. Segmental features (first formant frequency [F 1], second formant frequency [F 2], and vowel space area) and suprasegmental features (duration, intensity, and fundamental frequency [f o]) of vowel production were analyzed. Participants also categorized a vowel continuum synthesized from their own productions of /ɛ/ and /æ/ using HA, CI, and CI + HA.

RESULTS

F 1s of all vowels decreased; F 2s of front vowels but not back vowels increased; vowel space areas increased; and vowel durations, intensities, and f os decreased with statistical significance in the HA, CI, and CI + HA conditions relative to the ND condition. Only f os were lower, and vowel space areas were larger with CI and CI + HA than with HA. Average changes in f o, intensity, and F 1 from the ND condition to the HA, CI, and CI + HA conditions were positively correlated. Most participants did not show a typical psychometric function for vowel categorization, and thus, the relationship between vowel categorization and production was not tested.

CONCLUSIONS

The results suggest that acoustic, electric, and bimodal hearing have a measurable impact on vowel acoustics of post-lingually deaf adults when their hearing devices are turned on and off temporarily. Also, changes in f o and F 1 with the use of hearing devices may be largely driven by changes in intensity.

Speech Production Quality of Cochlear Implant Users with Respect to Duration and Onset of Hearing Loss

PURPOSE

To assess whether postlingual onset and shorter duration of deafness before cochlear implant (CI) provision predict higher speech intelligibility results of CI users.

METHODS

For an objective judgement of speech intelligibility, we used an automatic speech recognition system computing the word recognition rate (WR) of 50 adult CI users and 50 age-matched control individuals. All subjects were recorded reading a standardized text. Subjects were divided into three groups: pre- or perilingual deafness (A), both >2 years before implantation, postlingual deafness <2 years before implantation (B), or postlingual deafness >2 years before implantation (C).

RESULTS

CI users with short duration of postlingual deafness (B) had a significantly higher WR (median 74%) than CI users with long duration of postlingual deafness (C; 68%, p < 0.001) or pre-/perilingual onset (A; 56%, p < 0.001). Compared to their control groups only CI users with short duration of postlingual deafness reached similar WR, others showed significantly lower WR. Other factors such as hearing loss onset, duration of CI use, or duration of amplified hearing showed no consistent influence on speech quality.

CONCLUSIONS

The speech production quality of adult CI users shows dependencies on the onset and duration of deafness. These features need to be considered while planning rehabilitation.

The economic and societal benefits of adult cochlear implant implantation: A pilot exploratory study

BACKGROUND

Cochlear implantation has been shown to result in significant improvements in communication and quality of life, but little is known about the effect of cochlear implantation and changes in a person's employment status and earning potential. The purpose of this study is to measure the extent to which personal income changes in people who receive a cochlear implant.

METHODS

We mailed a survey to a random selection of 150 cochlear implantees who receive health services in a large urban setting. Of the 93 respondents, 65 were eligible for inclusion. Demographics, current income and income prior to implantation were recorded into income categories.

RESULTS

With a 6.6-year mean duration from cochlear implantation, it was found that 31% of respondents had increased income enough to move income brackets, with a mean category rise of $10 021. Forty participants reported working pre-implant, while 49 reported working post-implant.

IMPLICATIONS

Our results suggest preliminary evidence for an association between cochlear implantation and income. Increased accesses to cochlear implantation may provide opportunities for competitive employment and associated economic benefits for the individual, their families, and society.

Functional and structural aging of the speech sensorimotor neural system: functional magnetic resonance imaging evidence

The ability to perceive and produce speech undergoes important changes in late adulthood. The goal of the present study was to characterize functional and structural age-related differences in the cortical network that support speech perception and production, using magnetic resonance imaging, as well as the relationship between functional and structural age-related changes occurring in this network. We asked young and older adults to observe videos of a speaker producing single words (perception), and to observe and repeat the words produced (production). Results show a widespread bilateral network of brain activation for Perception and Production that was not correlated with age. In addition, several regions did show age-related change (auditory cortex, planum temporale, superior temporal sulcus, premotor cortices, SMA-proper). Examination of the relationship between brain signal and regional and global gray matter volume and cortical thickness revealed a complex set of relationships between structure and function, with some regions showing a relationship between structure and function and some not. The present results provide novel findings about the neurobiology of aging and verbal communication.

Spoken word recognition in adolescent cochlear implant users during quiet and multispeaker babble conditions

OBJECTIVE

To assess overall speech intelligibility in adolescent cochlear implant speakers during quiet and multispeaker babble conditions.

STUDY DESIGN

A cross-sectional assessment of intelligibility incorporating group (auditory-oral versus total communication speakers), sentence context (high versus low contexts), and background conditions (quiet versus multispeaker babble).

SETTING

A camp designed to assess adolescents over a concentrated period.

PARTICIPANTS

Fifty-seven adolescents who participated in an earlier study when they were 8 to 9 years old examining functional outcomes of speech perception, speech production, and language were asked to participate in follow-up study.

METHODS

Speech intelligibility was assessed by asking the adolescents to repeat sentences. Sentences were digitally edited and played to normal hearing listeners who either provided broad transcriptions of sound accuracy or wrote down the words they understood when the sentences were presented in quiet and in multispeaker babble.

MAIN OUTCOME VARIABLE

The dependent variables were percent correct consonants, vowels, and total words identified.

RESULTS

Very few substitutions or omissions occurred, resulting in high levels of accuracy for consonants and vowels. Speech intelligibility in quiet was significantly greater than in the multispeaker babble condition. Multispeaker babble decreased performance uniformly across sentence context for the 2 groups.

CONCLUSION

Accurate consonant production based on measures of substitutions and omissions fails to account for distortions and allophonic variations. Reductions in speech intelligibility relative to the phoneme correct productions suggest that the allophonic variations related to distortions may influence naive listener's ability to understand the speech of profoundly deaf individuals.

Speech intelligibility as a predictor of cochlear implant outcome in prelingually deafened adults

OBJECTIVES

Among adult patients with prelingual deafness, interindividual variability in speech perception outcome after cochlear implantation is generally large. It was hypothesized that the intelligibility of the patient's own speech may be predictive of speech perception with a cochlear implant. The objectives were (1) to provide a validation of a new test battery as a measurement tool for intelligibility using a group of prelingually deafened patients; (2) to investigate the validity of the test battery as a predictor of postimplant speech perception, based on preliminary data with a cochlear implant from a subgroup of patients; and (3) to investigate the validity of the test battery as a predictor of postimplant health-related quality of life (HRQoL) for the same subgroup of patients.

DESIGN

Twenty-five adult cochlear implant candidates with prelingual deafness participated in this study. Average age at onset of deafness was 8 mos (range 0 to 4 yrs). Speech samples from the participants were recorded and presented to two normal-hearing listeners. Results from the seven intelligibility tests in the battery were subjected to analyses of reliability and validity. Furthermore, the multiple test outcomes were submitted to a Principal Component Analysis to investigate the possibility of summarizing the data. Subsequently, from the group of 25 participants, 9 participants with above-average intelligibility were selected for implantation. Speech perception data with a cochlear implant from the nine implantees were collected at 12 mos postimplantation, as well as HRQoL data. Predictive validity of the intelligibility test battery was determined, using the postimplant data as the criterion.

RESULTS

Results from the 25 participants averaged over listeners showed that all tests in the battery had good reliability and validity as measures of intelligibility. Principal Component Analysis showed that the multiple test outcomes could be summarized by a single underlying variable. Despite the early age at onset of deafness, the subgroup of nine participants who received a cochlear implant included several good performers in terms of speech perception with the implant. The intelligibility test battery summary score had good validity as a predictor of postimplant outcome: the more intelligible the participant's speech, the better his or her speech perception outcome with the cochlear implant. Availability of effective auditory input in early life may be the fundamental factor underlying the potential for speech perception with a cochlear implant in later life. The intelligibility test battery can be reduced to a single test to minimize testing time without negatively affecting its predictive validity. Predictive validity of the intelligibility test battery can be generalized to HRQoL outcomes of cochlear implantation, provided these outcomes are concerned with speech processing abilities.

CONCLUSIONS

The new test battery (or its reduced version), used as a measure of intelligibility, is a promising tool for guiding cochlear implant candidacy decisions and counseling for individual patients with prelingual deafness. Because intelligibility has superior predictive power in comparison to age at onset of deafness, the latter should be discarded as an exclusion criterion for cochlear implantation.

Methodological aspects of assessing speech intelligibility among children with impaired hearing

OBJECTIVE

In the assessment of speech intelligibility, procedures that are easy to use, but also valid and reliable, are needed. The aim of this study was to explore the reliability and concurrent validity of two scaling methods for assessing the speech intelligibility of children with impaired hearing.

MATERIAL AND METHODS

A total of 51 children aged 4-17 years with a mild to profound hearing impairment performed a naming task comprising 62 single words. Altogether, 85 inexperienced listeners, divided into 17 panels, assessed the speech production of the children. A percent correct score (for identification of the words) was obtained from every listener. The listeners were also asked to judge the overall intelligibility of each child using a visual analogue scale (VAS) and a four-point ordinal level rating scale with verbal descriptors.

RESULTS

The percent correct score correlated significantly both with the VAS and the rating scale with verbal descriptors (Pearsons' coefficient 0.90 and Spearman's coefficient 0.78, respectively). Also, the VAS and the scale with verbal descriptors were significantly intercorrelated (Spearman's rho 0.85). Moderate to high correlations were usually obtained for all grades of hearing impairment, both sexes, different age groups and main communication modes.

CONCLUSIONS

Especially for assessing the need for remediation of speech and in monitoring its effectiveness, a quick overall estimate of speech intelligibility can be obtained quite reliably using the above rating scales. Item identification is more time-consuming but is often needed in research and therapy planning, where acoustic and linguistic phenomena that reduce intelligibility need to be traced.

Language-specific, hearing-related changes in vowel spaces: a preliminary study of English- and Spanish-speaking cochlear implant users

OBJECTIVE

This study investigates the role of hearing in vowel productions of postlingually deafened cochlear implant users. Two hypotheses are tested that derive from the view that vowel production is influenced by competing demands of intelligibility for the listener and least effort in the speaker: 1) Hearing enables a cochlear implant user to produce vowels distinctly from one another; without hearing, the speaker may give more weight to economy of effort, leading to reduced vowel separation. 2) Speakers may need to produce vowels more distinctly from one another in a language with a relatively "crowded" vowel space, such as American English, than in a language with relatively few vowels, such as Spanish. Thus, when switching between hearing and non-hearing states, English speakers may show a tradeoff between vowel distinctiveness and least effort, whereas Spanish speakers may not.

DESIGN

To test the prediction that there will be a reduction of average vowel spacing (AVS) (average intervowel distance in the F1-F2 plane) with interrupted hearing for English-speaking cochlear implant users, but no systematic change in AVS for Spanish cochlear implant users, vowel productions of seven English-speaking and seven Spanish-speaking cochlear implant users, who had been using their implants for at least 1 yr, were recorded when their implant speech processors were turned off and on several times in two sessions.

RESULTS

AVS was consistently larger for the English speakers with hearing than without hearing. The magnitude and direction of AVS change was more variable for the Spanish speakers, both within and between subjects.

CONCLUSION

Vowel distinctiveness was enhanced with the provision of some hearing in the language group with a more crowded vowel space but not in the language group with fewer vowels. The view that speakers seek to minimize effort while maintaining the distinctiveness of acoustic goals receives some support.

The effects of changes in hearing status in cochlear implant users on the acoustic vowel space and CV coarticulation

In order to examine the role of hearing status in controlling coarticulation, eight English vowels in /bVt/ and /dVt/ syllables, embedded in a carrier phrase, were elicited from 7 postlingually deafened adults and 2 speakers with normal hearing. The deaf adults served in repeated recording sessions both before and up to a year after they received cochlear implants and their speech processors were turned on. Each of the two hearing control speakers served in two recording sessions, separated by about 3 months. Measures were made of second formant frequency at obstruent release and at 25 ms intervals until the final obstruent. An index of coarticulation, based on the ratio of F2 at vowel onset to F2 at midvowel target, was computed. Changes in the amount of coarticulation after the change in hearing status were small and nonsystematic for the /bVt/ syllables; those for the /dVt/ syllables averaged a 3% increase--within the range of reliability measures for the 2 hearing control speakers. Locus equations (F2 at vowel onset vs. F2 at vowel midpoint) and ratios of F2 onsets in point vowels were also calculated. Like the index of coarticulation, these measures tended to confirm that hearing status had little if any effect on coarticulation in the deaf speakers, consistent with the hypothesis that hearing does not play a direct role in regulating anticipatory coarticulation in adulthood. With the restoration of some hearing, 2 implant users significantly increased the average spacing between vowels in the formant plane, whereas the remaining 5 decreased that measure. All speakers but one also reduced vowel duration significantly. Four of the speakers reduced dispersion of vowel formant values around vowel midpoint means, but the other 3 did not show this effect.