Moderate auditory training can improve speech performance of adult cochlear implant patients

Task-Specific Rapid Auditory Perceptual Learning in Adult Cochlear Implant Recipients: What Could It Mean for Speech Recognition

OBJECTIVES

Speech recognition in cochlear implant (CI) recipients is quite variable, particularly in challenging listening conditions. Demographic, audiological, and cognitive factors explain some, but not all, of this variance. The literature suggests that rapid auditory perceptual learning explains unique variance in speech recognition in listeners with normal hearing and those with hearing loss. The present study focuses on the early adaptation phase of task-specific rapid auditory perceptual learning. It investigates whether adult CI recipients exhibit this learning and, if so, whether it accounts for portions of the variance in their recognition of fast speech and speech in noise.

DESIGN

Thirty-six adult CI recipients (ages = 35 to 77, M = 55) completed a battery of general speech recognition tests (sentences in speech-shaped noise, four-talker babble noise, and natural-fast speech), cognitive measures (vocabulary, working memory, attention, and verbal processing speed), and a rapid auditory perceptual learning task with time-compressed speech. Accuracy in the general speech recognition tasks was modeled with a series of generalized mixed models that accounted for demographic, audiological, and cognitive factors before accounting for the contribution of task-specific rapid auditory perceptual learning of time-compressed speech.

RESULTS

Most CI recipients exhibited early task-specific rapid auditory perceptual learning of time-compressed speech within the course of the first 20 sentences. This early task-specific rapid auditory perceptual learning had unique contribution to the recognition of natural-fast speech in quiet and speech in noise, although the contribution to natural-fast speech may reflect the rapid learning that occurred in this task. When accounting for demographic and cognitive characteristics, an increase of 1 SD in the early task-specific rapid auditory perceptual learning rate was associated with ~52% increase in the odds of correctly recognizing natural-fast speech in quiet, and ~19% to 28% in the odds of correctly recognizing the different types of speech in noise. Age, vocabulary, attention, and verbal processing speed also had unique contributions to general speech recognition. However, their contribution varied between the different general speech recognition tests.

CONCLUSIONS

Consistent with previous findings in other populations, in CI recipients, early task-specific rapid auditory perceptual, learning also accounts for some of the individual differences in the recognition of speech in noise and natural-fast speech in quiet. Thus, across populations, the early rapid adaptation phase of task-specific rapid auditory perceptual learning might serve as a skill that supports speech recognition in various adverse conditions. In CI users, the ability to rapidly adapt to ongoing acoustical challenges may be one of the factors associated with good CI outcomes. Overall, CI recipients with higher cognitive resources and faster rapid learning rates had better speech recognition.

Effects of training length on adaptation to noise-vocoded speech

Listeners show rapid perceptual learning of acoustically degraded speech, though the amount of exposure required to maximize speech adaptation is unspecified. The current work used a single-session design to examine the length of auditory training on perceptual learning for normal hearing listeners exposed to eight-channel noise-vocoded speech. Participants completed short, medium, or long training using a two-alternative forced choice sentence identification task with feedback. To assess learning and generalization, a 40-trial pre-test and post-test transcription task was administered using trained and novel sentences. Training results showed all groups performed near ceiling with no reliable differences. For test data, we evaluated changes in transcription accuracy using separate linear mixed models for trained or novel sentences. In both models, we observed a significant improvement in transcription at post-test relative to pre-test. Critically, the three training groups did not differ in the magnitude of improvement following training. Subsequent Bayes factors analysis evaluating the test by group interaction provided strong evidence in support of the null hypothesis. For these stimuli and procedure, results suggest increased training does not necessarily maximize learning outcomes; both passive and trained experience likely supported adaptation. Findings may contribute to rehabilitation recommendations for listeners adapting to degraded speech signals.

Preliminary evaluation of computer-assisted home training for French cochlear implant recipients

For French cochlear implant (CI) recipients, in-person clinical auditory rehabilitation is typically provided during the first few years post-implantation. However, this is often inconvenient, it requires substantial time resources and can be problematic when appointments are unavailable. In response, we developed a computer-based home training software ("French AngelSound™") for French CI recipients. We recently conducted a pilot study to evaluate the newly developed French AngelSound™ in 15 CI recipients (5 unilateral, 5 bilateral, 5 bimodal). Outcome measures included phoneme recognition in quiet and sentence recognition in noise. Unilateral CI users were tested with the CI alone. Bilateral CI users were tested with each CI ear alone to determine the poorer ear to be trained, as well as with both ears (binaural performance). Bimodal CI users were tested with the CI ear alone, and with the contralateral hearing aid (binaural performance). Participants trained at home over a one-month period (10 hours total). Phonemic contrast training was used; the level of difficulty ranged from phoneme discrimination in quiet to phoneme identification in multi-talker babble. Unilateral and bimodal CI users trained with the CI alone; bilateral CI users trained with the poorer ear alone. Outcomes were measured before training (pre-training), immediately after training was completed (post-training), and one month after training was stopped (follow-up). For all participants, post-training CI-only vowel and consonant recognition scores significantly improved after phoneme training with the CI ear alone. For bilateral and bimodal CI users, binaural vowel and consonant recognition scores also significantly improved after training with a single CI ear. Follow-up measures showed that training benefits were largely retained. These preliminary data suggest that the phonemic contrast training in French AngelSound™ may significantly benefit French CI recipients and may complement clinical auditory rehabilitation, especially when in-person visits are not possible.

Comparing the Outcomes of a Personalized Versus Nonpersonalized Home-Based Auditory Training Program for Cochlear Implant Users

OBJECTIVES

Audiological rehabilitation includes sensory management, auditory training (AT), and counseling and can alleviate the negative consequences associated with (untreated) hearing impairment. AT aims at improving auditory skills through structured analytical (bottom-up) or synthetic (top-down) listening exercises. The evidence for AT to improve auditory outcomes of postlingually deafened adults with a cochlear implant (CI) remains a point of debate due to the relatively limited number of studies and methodological shortcomings. There is a general agreement that more rigorous scientific study designs are needed to determine the effectiveness, generalization, and consolidation of AT for CI users. The present study aimed to investigate the effectiveness of a personalized AT program compared to a nonpersonalized Active Control program with adult CI users in a stratified randomized controlled clinical trial.

DESIGN

Off-task outcomes were sentence understanding in noise, executive functioning, and health-related quality of life. Participants were tested before and after 16 weeks of training and after a further 8 months without training. Participant expectations of the training program were assessed before the start of training.

RESULTS

The personalized and nonpersonalized AT programs yielded similar results. Significant on-task improvements were observed. Moreover, AT generalized to improved speech understanding in noise for both programs. Half of the CI users reached a clinically relevant improvement in speech understanding in noise of at least 2 dB SNR post-training. These improvements were maintained 8 months after completion of the training. In addition, a significant improvement in quality of life was observed for participants in both treatment groups. Adherence to the training programs was high, and both programs were considered user-friendly.

CONCLUSIONS

Training in both treatments yielded similar results. For half of the CI users, AT transferred to better performance with generalization of learning for speech understanding in noise and quality of life. Our study supports the previous findings that AT can be beneficial for some CI users.

Many tasks, same outcome: Role of training task on learning and maintenance of noise-vocoded speech

Listeners who use cochlear implants show variability in speech recognition. Research suggests that structured auditory training can improve speech recognition outcomes in cochlear implant users, and a central goal in the rehabilitation literature is to identify factors that maximize training. Here, we examined factors that may influence perceptual learning for noise-vocoded speech in normal hearing listeners as a foundational step towards clinical recommendations. Three groups of listeners were exposed to anomalous noise-vocoded sentences and completed one of three training tasks: transcription with feedback, transcription without feedback, or talker identification. Listeners completed a word transcription test at three time points: immediately before training, immediately after training, and one week following training. Accuracy at test was indexed by keyword accuracy at the sentence-initial and sentence-final position for high and low predictability noise-vocoded sentences. Following training, listeners showed improved transcription for both sentence-initial and sentence-final items, and for both low and high predictability sentences. The training groups showed robust and equivalent learning of noise-vocoded sentences immediately after training. Critically, gains were largely maintained equivalently among training groups one week later. These results converge with evidence pointing towards the utility of non-traditional training tasks to maximize perceptual learning of noise-vocoded speech.

Effect of Serious Gaming on Speech-in-Noise Intelligibility in Adult Cochlear Implantees: A Randomized Controlled Study

Listening in noise remains challenging for adults with cochlear implants (CI) even after prolonged experience. Personalized auditory training (AT) programs can be proposed to improve specific auditory skills in adults with CI. The objective of this study was to assess serious gaming as a rehabilitation tool to improve speech-in-noise intelligibility in adult CI users. Thirty subjects with bilateral profound hearing loss and at least 9 months of CI experience were randomized to participate in a 5-week serious game-based AT program (n = 15) or a control group (n = 15). All participants were tested at enrolment and at 5 weeks using the sentence recognition-in-noise matrix test to measure the signal-to-noise ratio (SNR) allowing 70% of speech-in-noise understanding (70% speech reception threshold, SRT70). Thirteen subjects completed the AT program and nine of them were re-tested 5 weeks later. The mean SRT70 improved from 15.5 dB to 11.5 dB SNR after 5 weeks of AT (p < 0.001). No significant change in SRT70 was observed in the control group. In the study group, the magnitude of SRT70 improvement was not correlated to the total number of AT hours. A large inter-patient variability was observed for speech-in-noise intelligibility measured once the AT program was completed and at re-test. The results suggest that serious game-based AT may improve speech-in-noise intelligibility in adult CI users. Potential sources of inter-patient variability are discussed. Serious gaming may be considered as a complementary training approach for improving CI outcomes in adults.

Cochlear Implant Research and Development in the Twenty-first Century: A Critical Update

Cochlear implants (CIs) are the world's most successful sensory prosthesis and have been the subject of intense research and development in recent decades. We critically review the progress in CI research, and its success in improving patient outcomes, from the turn of the century to the present day. The review focuses on the processing, stimulation, and audiological methods that have been used to try to improve speech perception by human CI listeners, and on fundamental new insights in the response of the auditory system to electrical stimulation. The introduction of directional microphones and of new noise reduction and pre-processing algorithms has produced robust and sometimes substantial improvements. Novel speech-processing algorithms, the use of current-focusing methods, and individualised (patient-by-patient) deactivation of subsets of electrodes have produced more modest improvements. We argue that incremental advances have and will continue to be made, that collectively these may substantially improve patient outcomes, but that the modest size of each individual advance will require greater attention to experimental design and power. We also briefly discuss the potential and limitations of promising technologies that are currently being developed in animal models, and suggest strategies for researchers to collectively maximise the potential of CIs to improve hearing in a wide range of listening situations.

Tablet-Based Telerehabilitation Versus Conventional Face-to-Face Rehabilitation After Cochlear Implantation: Prospective Intervention Pilot Study

Background

Technologies allowing home-based rehabilitation may be a key means of saving financial resources while also facilitating people’s access to treatment. After cochlear implantation, auditory training is necessary for the brain to adapt to new auditory signals transmitted by the cochlear implant (CI). To date, auditory training is conducted in a face-to-face setting at a specialized center. However, because of the COVID-19 pandemic’s impact on health care, the need for new therapeutic settings has intensified.

Objective

The aims of this study are to assess the feasibility of a novel teletherapeutic auditory rehabilitation platform in adult CI recipients and compare the clinical outcomes and economic benefits of this platform with those derived from conventional face-to-face rehabilitation settings in a clinic.

Methods

In total, 20 experienced adult CI users with a mean age of 59.4 (SD 16.3) years participated in the study. They completed 3 weeks of standard (face-to-face) therapy, followed by 3 weeks of computer-based auditory training (CBAT) at home. Participants were assessed at three intervals: before face-to-face therapy, after face-to-face therapy, and after CBAT. The primary outcomes were speech understanding in quiet and noisy conditions. The secondary outcomes were the usability of the CBAT system, the participants’ subjective rating of their own listening abilities, and the time required for completing face-to-face and CBAT sessions for CI users and therapists.

Results

Greater benefits were observed after CBAT than after standard therapy in nearly all speech outcome measures. Significant improvements were found in sentence comprehension in noise (P=.004), speech tracking (P=.004) and phoneme differentiation (vowels: P=.001; consonants: P=.02) after CBAT. Only speech tracking improved significantly after conventional therapy (P=.007). The program’s usability was judged to be high: only 2 of 20 participants could not imagine using the program without support. The different features of the training platform were rated as high. Cost analysis showed a cost difference in favor of CBAT: therapists spent 120 minutes per week face-to-face and 30 minutes per week on computer-based sessions. For CI users, attending standard therapy required an average of approximately 78 (SD 58.6) minutes of travel time per appointment.

Conclusions

The proposed teletherapeutic approach for hearing rehabilitation enables good clinical outcomes while saving time for CI users and clinicians. The promising speech understanding results might be due to the high satisfaction of users with the CBAT program. Teletherapy might offer a cost-effective solution to address the lack of human resources in health care as well as the global challenge of current or future pandemics.

Development of cortical auditory responses to speech in noise in unilaterally deaf adults following cochlear implantation

BACKGROUND

For patients with single-sided deafness (SSD), restoration of binaural function via cochlear implant (CI) has been shown to improve speech understanding in noise. The objective of this study was to investigate changes in behavioral performance and cortical auditory responses following cochlear implantation.

DESIGN

Prospective longitudinal study.

SETTING

Tertiary referral center.

METHODS

Six adults with SSD were tested before and 12 months post-activation of the CI. Six normal hearing (NH) participants served as experimental controls. Speech understanding in noise was evaluated for various spatial conditions. Cortical auditory evoked potentials were recorded with /ba/ stimuli in quiet and in noise. Global field power and responses at Cz were analyzed.

RESULTS

Speech understanding in noise significantly improved with the CI when speech was presented to the CI ear and noise to the normal ear (p<0.05), but remained poorer than that of NH controls (p<0.05). N1 peak amplitude measure in noise significantly increased after CI activation (p<0.05), but remained lower than that of NH controls (p<0.05) at 12 months. After 12 months of CI experience, cortical responses in noise became more comparable between groups.

CONCLUSION

Binaural restoration in SSD patients via cochlear implantation improved speech performance noise and cortical responses. While behavioral performance and cortical auditory responses improved, SSD-CI outcomes remained poorer than that of NH controls in most cases, suggesting only partial restoration of binaural hearing.

[Computer-based auditory training for hearing rehabilitation of adult cochlear implant users]

BACKGROUND

Digitalization has become a part of everyday life and digital applications offer an opportunity to promote health. In Germany, hearing rehabilitation after cochlear implantation (CI) typically takes place in specialized audiology centers. However, a variety of new auditory training programs have been developed and although most are for hearing aid users, some are suitable for CI patients. The purpose of this study is to give an overview of CBAT schedules and their effectiveness.

MATERIALS AND METHODS

Currently available English and German CBAT programs for adult CI users identified in searches of Google, Google App Store, and Google Play Store were analyzed. A systematic literature search on studies dealing with CBAT in adult CI recipients from 2000 to 2019 was performed in PubMed, LIVIVO, and Google Scholar.

RESULTS

German and English CBAT for adult hearing aid and CI users are generally intended to complement face-to-face therapies. The content of the programs differs primarily in terms of complexity and quantity of tasks, graphic design, allowed time and the device used. In contrast to the nine available German programs, some of the English CBAT include advanced concepts of adaptivity and feedback. Studies on the effectiveness of CBAT have mainly been conducted for the English versions and generally analyze only individual therapeutic subfunctions. All investigations show a short-term improvement of the auditory subfunction shortly after training. Unfortunately, the quality of the studies is low and follow-up results are only available in two cases.

CONCLUSION

CBAT programs might be an effective option for auditory rehabilitation in CI patients. However, suitable German-language programs conceived as an alternative to face-to-face training and studies on longterm effects of CBAT are still lacking.

Computer-Based Connected-Text Training of Speech-in-Noise Perception for Cochlear Implant Users

An interactive method for training speech perception in noise was assessed with adult cochlear implant users. The method employed recordings of connected narratives divided into phrases of 4 to 10 words, presented in babble. After each phrase, the listener identified key words from the phrase from among similar sounding foil words. Nine postlingually deafened adult cochlear implant users carried out 12 hr of training over a 4-week period. Training was carried out at home on tablet computers. The primary outcome measure was sentence recognition in babble. Vowel and consonant identification in speech-shaped noise were also assessed, along with digit span in noise, intended as a measure of some important underlying cognitive abilities. Talkers for speech tests were different from those used in training. To control for procedural learning, the test battery was administered repeatedly prior to training. Performance was assessed immediately after training and again after a further 4 weeks during which no training occurred. Sentence recognition in babble improved significantly after training, with an improvement in speech reception threshold of approximately 2 dB, which was maintained at the 4-week follow-up. There was little evidence of improvement in the other measures. It appears that the method has potential as a clinical intervention. However, the underlying sources of improvement and the extent to which benefits generalize to real-world situations remain to be determined.

Learning of Artificial Sensation Through Long-Term Home Use of a Sensory-Enabled Prosthesis

Upper limb prostheses are specialized tools, and skilled operation is learned by amputees over time. Recently, neural prostheses using implanted peripheral nerve interfaces have enabled advances in artificial somatosensory feedback that can improve prosthesis outcomes. However, the effect of sensory learning on artificial somatosensation has not been studied, despite its known influence on intact somatosensation and analogous neuroprostheses. Sensory learning involves changes in the perception and interpretation of sensory feedback and may further influence functional and psychosocial outcomes. In this mixed methods case study, we examined how passive learning over 115 days of home use of a neural-connected, sensory-enabled prosthetic hand influenced perception of artificial sensory feedback in a participant with transradial amputation. We examined perceptual changes both within individual days of use and across the duration of the study. At both time scales, the reported percept locations became significantly more aligned with prosthesis sensor locations, and the phantom limb became significantly more extended toward the prosthesis position. Similarly, the participant’s ratings of intensity, naturalness, and contact touch significantly increased, while his ratings of vibration and movement significantly decreased across-days for tactile channels. These sensory changes likely resulted from engagement of cortical plasticity mechanisms as the participant learned to use the artificial sensory feedback. We also assessed psychosocial and functional outcomes through surveys and interviews, and found that self-efficacy, perceived function, prosthesis embodiment, social touch, body image, and prosthesis efficiency improved significantly. These outcomes typically improved within the first month of home use, demonstrating rapid benefits of artificial sensation. Participant interviews indicated that the naturalness of the experience and engagement with the prosthesis increased throughout the study, suggesting that artificial somatosensation may decrease prosthesis abandonment. Our data showed that prosthesis embodiment was intricately related to naturalness and phantom limb perception, and that learning the artificial sensation may have modified the body schema. As another indicator of successfully learning to use artificial sensation, the participant reported the emergence of stereognosis later in the study. This study provides the first evidence that artificial somatosensation can undergo similar learning processes as intact sensation and highlights the importance of sensory restoration in prostheses.

A Randomized Controlled Crossover Study of the Impact of Online Music Training on Pitch and Timbre Perception in Cochlear Implant Users

Cochlear implant (CI) biomechanical constraints result in impoverished spectral cues and poor frequency resolution, making it difficult for users to perceive pitch and timbre. There is emerging evidence that music training may improve CI-mediated music perception; however, much of the existing studies involve time-intensive and less readily accessible in-person music training paradigms, without rigorous experimental control paradigms. Online resources for auditory rehabilitation remain an untapped potential resource for CI users. Furthermore, establishing immediate value from an acute music training program may encourage CI users to adhere to post-implantation rehabilitation exercises. In this study, we evaluated the impact of an acute online music training program on pitch discrimination and timbre identification. Via a randomized controlled crossover study design, 20 CI users and 21 normal hearing (NH) adults were assigned to one of two arms. Arm-A underwent 1 month of online self-paced music training (intervention) followed by 1 month of audiobook listening (control). Arm-B underwent 1 month of audiobook listening followed by 1 month of music training. Pitch and timbre sensitivity scores were taken across three visits: (1) baseline, (2) after 1 month of intervention, and (3) after 1 month of control. We found that performance improved in pitch discrimination among CI users and NH listeners, with both online music training and audiobook listening. Music training, however, provided slightly greater benefit for instrument identification than audiobook listening. For both tasks, this improvement appears to be related to both fast stimulus learning as well as procedural learning. In conclusion, auditory training (with either acute participation in an online music training program or audiobook listening) may improve performance on untrained tasks of pitch discrimination and timbre identification. These findings demonstrate a potential role for music training in perceptual auditory appraisal of complex stimuli. Furthermore, this study highlights the importance and the need for more tightly controlled training studies in order to accurately evaluate the impact of rehabilitation training protocols on auditory processing.

Inducing musical-interval learning by combining task practice with periods of stimulus exposure alone

A key component of musical proficiency is the ability to discriminate between and identify musical intervals, or fixed ratios between pitches. Acquiring these skills requires training, but little is known about how to best arrange the trials within a training session. To address this issue, learning on a musical-interval comparison task was evaluated for two four-day training regimens that employed equal numbers of stimulus presentations per day. A regimen of continuous practice yielded no learning, but a regimen that combined practice and stimulus exposure alone generated clear improvement. Learning in the practice-plus-exposure regimen was due to the combination of the two experiences, because two control groups who received only either the practice or the exposure from that regimen did not learn. Posttest performance suggested that this improvement in comparison learning generalized to an untrained stimulus type and an untrained musical-interval identification task. Naïve comparison performance, but not learning, was better for larger pitch-ratio differences and for individuals with more musical experience. The reported benefits of the practice-plus-exposure regimen mirror the outcomes for fine-grained discrimination and speech tasks, suggesting that a general learning principle is involved. In practical terms, it appears that combining practice and stimulus exposure alone is a particularly effective configuration for improving musical-interval perception.

Word Recognition Variability With Cochlear Implants: The Degradation of Phonemic Sensitivity

OBJECTIVE

Cochlear implants (CIs) do not automatically restore speech recognition for postlingually deafened adults. Average word recognition remains at 60%, and enormous variability exists. Understanding speech requires knowledge of phonemic codes, the basic sound units of language. Hearing loss may result in degeneration of these long-term mental representations (i.e., "phonemic sensitivity"), and CI use may not adequately restore those representations. This investigation examined whether phonemic sensitivity is degraded for CI users, and whether this degradation results in poorer word recognition.

STUDY DESIGN

Thirty adults with CIs and 20 normal-hearing controls underwent testing.

METHODS

Participants were assessed for word recognition in quiet, along with tasks of phonemic sensitivity using an audiovisual format to maximize recognition: initial consonant choice (ICC), in which they selected the word with the same starting sound as a target word, final consonant choice (FCC), in which they selected the word with the same ending sound, and backwards words, in which they repeated phonemes comprising words in backwards order.

RESULTS

Phonemic sensitivity was poorer for CI users than for normal-hearing controls for ICC and FCC. For CI users, ICC and FCC predicted 25% and 40% of variance in word recognition, respectively. Longer duration of CI use did not lead to greater restoration in phonemic sensitivity.

CONCLUSION

Even for adults who presumably had developed refined phonemic representations, hearing loss can degrade those representations, which results in poorer word recognition. Cochlear implants do not adequately restore those representations. Findings suggest the need for rehabilitative efforts to improve CI users' phonemic sensitivity.

Efficacy of Multiple-Talker Phonetic Identification Training in Postlingually Deafened Cochlear Implant Listeners

PURPOSE

This study implemented a pretest-intervention-posttest design to examine whether multiple-talker identification training enhanced phonetic perception of the /ba/-/da/ and /wa/-/ja/ contrasts in adult listeners who were deafened postlingually and have cochlear implants (CIs).

METHOD

Nine CI recipients completed 8 hours of identification training using a custom-designed training package. Perception of speech produced by familiar talkers (talkers used during training) and unfamiliar talkers (talkers not used during training) was measured before and after training. Five additional untrained CI recipients completed identical pre- and posttests over the same time course as the trainees to control for procedural learning effects.

RESULTS

Perception of the speech contrasts produced by the familiar talkers significantly improved for the trained CI listeners, and effects of perceptual learning transferred to unfamiliar talkers. Such training-induced significant changes were not observed in the control group.

CONCLUSION

The data provide initial evidence of the efficacy of the multiple-talker identification training paradigm for CI users who were deafened postlingually. This pattern of results is consistent with enhanced phonemic categorization of the trained speech sounds.

Speech perception enhancement in elderly hearing aid users using an auditory training program for mobile devices

AIMS

The goal of the present study was to develop an auditory training program using a mobile device and to test its efficacy by applying it to older adults suffering from moderate-to-severe sensorineural hearing loss.

METHODS

Among the 20 elderly hearing-impaired listeners who participated, 10 were randomly assigned to a training group (TG) and 10 were assigned to a non-training group (NTG) as a control. As a baseline, all participants were measured by vowel, consonant and sentence tests. In the experiment, the TG had been trained for 4 weeks using a mobile program, which had four levels and consisted of 10 Korean nonsense syllables, with each level completed in 1 week. In contrast, traditional auditory training had been provided for the NTG during the same period. To evaluate whether a training effect was achieved, the two groups also carried out the same tests as the baseline after completing the experiment.

RESULTS

The results showed that performance on the consonant and sentence tests in the TG was significantly increased compared with that of the NTG. Also, improved scores of speech perception were retained at 2 weeks after the training was completed. However, vowel scores were not changed after the 4-week training in both the TG and the NTG.

CONCLUSIONS

This result pattern suggests that a moderate amount of auditory training using the mobile device with cost-effective and minimal supervision is useful when it is used to improve the speech understanding of older adults with hearing loss. Geriatr Gerontol Int 2017; 17: 61-68.

Speech perception in older hearing impaired listeners: benefits of perceptual training

Hearing aids (HAs) only partially restore the ability of older hearing impaired (OHI) listeners to understand speech in noise, due in large part to persistent deficits in consonant identification. Here, we investigated whether adaptive perceptual training would improve consonant-identification in noise in sixteen aided OHI listeners who underwent 40 hours of computer-based training in their homes. Listeners identified 20 onset and 20 coda consonants in 9,600 consonant-vowel-consonant (CVC) syllables containing different vowels (/ɑ/, /i/, or /u/) and spoken by four different talkers. Consonants were presented at three consonant-specific signal-to-noise ratios (SNRs) spanning a 12 dB range. Noise levels were adjusted over training sessions based on d’ measures. Listeners were tested before and after training to measure (1) changes in consonant-identification thresholds using syllables spoken by familiar and unfamiliar talkers, and (2) sentence reception thresholds (SeRTs) using two different sentence tests. Consonant-identification thresholds improved gradually during training. Laboratory tests of d’ thresholds showed an average improvement of 9.1 dB, with 94% of listeners showing statistically significant training benefit. Training normalized consonant confusions and improved the thresholds of some consonants into the normal range. Benefits were equivalent for onset and coda consonants, syllables containing different vowels, and syllables presented at different SNRs. Greater training benefits were found for hard-to-identify consonants and for consonants spoken by familiar than unfamiliar talkers. SeRTs, tested with simple sentences, showed less elevation than consonant-identification thresholds prior to training and failed to show significant training benefit, although SeRT improvements did correlate with improvements in consonant thresholds. We argue that the lack of SeRT improvement reflects the dominant role of top-down semantic processing in processing simple sentences and that greater transfer of benefit would be evident in the comprehension of more unpredictable speech material.

Benefits of music training in mandarin-speaking pediatric cochlear implant users

PURPOSE

The aims of this study were to assess young (5- to 10-year-old) Mandarin-speaking cochlear implant (CI) users' musical pitch perception and to assess the benefits of computer-based home training on performance.

METHOD

Melodic contour identification (MCI) was used to assess musical pitch perception in 14 Mandarin-speaking pediatric CI users; the instrument timbre and the contour length were varied as experimental parameters. Six subjects received subsequent MCI training on their home computer in which auditory and visual feedback were provided.

RESULTS

MCI performance was generally poor (grand mean=33.3% correct) and highly variable, with scores ranging from 9.3% to 98.1% correct; there was no significant effect of instrument timbre or contour length on performance (p>.05). After 4 weeks of training, performance sharply improved. Follow-up measures that were conducted 8 weeks after training was stopped showed no significant decline in MCI performance. For the 6 trained subjects, there was a significant effect of contour length for the training and follow-up measures.

CONCLUSION

These preliminary data suggest that although baseline MCI performance initially may be poor, training may greatly improve Mandarin-speaking pediatric CI users' melodic pitch perception.

Computer-based auditory phoneme discrimination training improves speech recognition in noise in experienced adult cochlear implant listeners

OBJECTIVE

Specific computer-based auditory training may be a useful completion in the rehabilitation process for cochlear implant (CI) listeners to achieve sufficient speech intelligibility. This study evaluated the effectiveness of a computerized, phoneme-discrimination training programme.

DESIGN

The study employed a pretest-post-test design; participants were randomly assigned to the training or control group. Over a period of three weeks, the training group was instructed to train in phoneme discrimination via computer, twice a week. Sentence recognition in different noise conditions (moderate to difficult) was tested pre- and post-training, and six months after the training was completed. The control group was tested and retested within one month.

STUDY SAMPLE

Twenty-seven adult CI listeners who had been using cochlear implants for more than two years participated in the programme; 15 adults in the training group, 12 adults in the control group.

RESULTS

Besides significant improvements for the trained phoneme-identification task, a generalized training effect was noted via significantly improved sentence recognition in moderate noise. No significant changes were noted in the difficult noise conditions. Improved performance was maintained over an extended period.

CONCLUSIONS

Phoneme-discrimination training improves experienced CI listeners' speech perception in noise. Additional research is needed to optimize auditory training for individual benefit.

Hear here: children with hearing loss learn words by listening

OBJECTIVES

Early use of hearing devices and family participation in auditory-verbal therapy has been associated with age-appropriate verbal communication outcomes for children with hearing loss. However, there continues to be great variability in outcomes across different oral intervention programmes and little consensus on how therapists should prioritise goals at each therapy session for positive clinical outcomes. This pilot intervention study aimed to determine whether therapy goals that concentrate on teaching preschool children with hearing loss how to distinguish between words in a structured listening programme is effective, and whether gains in speech perception skills impact on vocabulary and speech development without them having to be worked on directly in therapy.

METHOD

A multiple baseline across subjects design was used in this within-subject controlled study. 3 children aged between 2:6 and 3:1 with moderate-severe to severe-profound hearing loss were recruited for a 6-week intervention programme. Each participant commenced at different stages of the 10-staged listening programme depending on their individual listening skills at recruitment. Speech development and vocabulary assessments were conducted before and after the training programme in addition to speech perception assessments and probes conducted throughout the intervention programme.

RESULTS

All participants made gains in speech perception skills as well as vocabulary and speech development. Speech perception skills acquired were noted to be maintained a week after intervention. In addition, all participants were able to generalise speech perception skills learnt to words that had not been used in the intervention programme.

CONCLUSIONS

This pilot study found that therapy directed at listening alone is promising and that it may have positive impact on speech and vocabulary development without these goals having to be incorporated into a therapy programme. Although a larger study is necessary for more conclusive findings, the results from this preliminary study are promising in support of emphasise on listening skills within auditory-verbal therapy programmes.

Perceptual learning of temporally interrupted spectrally degraded speech

Normal-hearing (NH) listeners make use of context, speech redundancy and top-down linguistic processes to perceptually restore inaudible or masked portions of speech. Previous research has shown poorer perception and restoration of interrupted speech in CI users and NH listeners tested with acoustic simulations of CIs. Three hypotheses were investigated: (1) training with CI simulations of interrupted sentences can teach listeners to use the high-level restoration mechanisms more effectively, (2) phonemic restoration benefit, an increase in intelligibility of interrupted sentences once its silent gaps are filled with noise, can be induced with training, and (3) perceptual learning of interrupted sentences can be reflected in clinical speech audiometry. To test these hypotheses, NH listeners were trained using periodically interrupted sentences, also spectrally degraded with a noiseband vocoder as CI simulation. Feedback was presented by displaying the sentence text and playing back both the intact and the interrupted CI simulation of the sentence. Training induced no phonemic restoration benefit, and learning was not transferred to speech audiometry measured with words. However, a significant improvement was observed in overall intelligibility of interrupted spectrally degraded sentences, with or without filler noise, suggesting possibly better use of restoration mechanisms as a result of training.

The effects of short-term computerized speech-in-noise training on postlingually deafened adult cochlear implant recipients

PURPOSE

To determine if short-term computerized speech-in-noise training can produce significant improvements in speech-in-noise perception by cochlear implant (CI) recipients on standardized audiologic testing measures.

METHOD

Five adult postlingually deafened CI recipients participated in 4 speech-in-noise training sessions using the Seeing and Hearing Speech program (Sensimetrics; Malden, MA). Each participant completed lessons concentrating on consonant and vowel recognition at word, phrase, and sentence levels. Speech-in-noise abilities were assessed using the QuickSIN (Killion, Niquette, Gudmundsen, Revit, & Banerjee, 2004) and the Hearing in Noise Test (HINT ( Nilsson, Soli & Sullivan, 1994)).

RESULTS

All listeners significantly improved key word identification on the HINT after training, albeit only at the most favorable signal-to-noise ratio (SNR). Listeners also showed a significant reduction in the degree of SNR loss on the QuickSIN after training.

CONCLUSION

Short-term speech-in-noise training may improve speech-in-noise perception in postlingually deafened adult CI recipients.

Comparing live to recorded speech in training the perception of spectrally shifted noise-vocoded speech

Two experimental groups were trained for 2 h with live or recorded speech that was noise-vocoded and spectrally shifted and was from the same text and talker. These two groups showed equivalent improvements in performance for vocoded and shifted sentences, and the group trained with recorded speech showed consistently greater improvements than untrained controls. Another group trained with unshifted noise-vocoded speech improved no more than untrained controls. Computer-based training thus appears at least as effective as labor-intensive live-voice training for improving the perception of spectrally shifted noise-vocoded speech, and by implication, for training of users of cochlear implants.

Talker-identification training using simulations of binaurally combined electric and acoustic hearing: generalization to speech and emotion recognition

Understanding speech in background noise, talker identification, and vocal emotion recognition are challenging for cochlear implant (CI) users due to poor spectral resolution and limited pitch cues with the CI. Recent studies have shown that bimodal CI users, that is, those CI users who wear a hearing aid (HA) in their non-implanted ear, receive benefit for understanding speech both in quiet and in noise. This study compared the efficacy of talker-identification training in two groups of young normal-hearing adults, listening to either acoustic simulations of unilateral CI or bimodal (CI+HA) hearing. Training resulted in improved identification of talkers for both groups with better overall performance for simulated bimodal hearing. Generalization of learning to sentence and emotion recognition also was assessed in both subject groups. Sentence recognition in quiet and in noise improved for both groups, no matter if the talkers had been heard during training or not. Generalization to improvements in emotion recognition for two unfamiliar talkers also was noted for both groups with the simulated bimodal-hearing group showing better overall emotion-recognition performance. Improvements in sentence recognition were retained a month after training in both groups. These results have potential implications for aural rehabilitation of conventional and bimodal CI users.

Relative importance of monaural sound deprivation and bilateral significant hearing loss in predicting cochlear implantation outcomes

OBJECTIVES

Making evidence-based recommendations to prospective unilateral cochlear implant recipients on the potential benefits of implanting one or the other ear is challenging for cochlear implant teams. This particularly occurs in cases where a hearing aid has only been used in one ear for many years (referred to here as the "hearing ear"), and the contralateral ear has, in essence, been sound-deprived. In such cases, research to date is inconclusive, and little anecdotal evidence exists to inform the debate and support best clinical practice.

DESIGN

Retrospective data on speech recognition outcomes of 16 adult participants who received a cochlear implant in an ear deprived of sound for a minimum of 15 yr were analyzed. All subjects were implanted through the Quebec Cochlear Implant Program and were provided with personalized intensive rehabilitation services. Data obtained from clinical records included demographic data and speech recognition scores measured after implantation with the sentences of a multimedia auditory test battery in the auditory-only condition. Speech recognition outcomes were compared with the duration of auditory deprivation in the implanted ear, bilateral significant hearing loss, and auditory stimulation before bilateral significant hearing loss.

RESULTS

Using nonparametric correlation analyses, a strong negative correlation was demonstrated between speech recognition scores and the duration of bilateral significant hearing loss and with the duration of auditory stimulation before bilateral significant hearing loss. No significant correlation with the duration of auditory deprivation or with the duration of prior auditory stimulation in the implanted ear was found.

CONCLUSIONS

These findings suggest that functional outcomes of cochlear implantation for unilateral sound deprivation may be more strongly influenced by central processes than peripheral effects stemming from the deprivation per se. This indicates the relevance of considering the client's history of binaural hearing rather than the hearing in each ear individually when discussing possible outcomes with a cochlear implant.

Resistance to learning binaurally mismatched frequency-to-place maps: implications for bilateral stimulation with cochlear implants

Simulations of monaural cochlear implants in normal hearing listeners have shown that the deleterious effects of upward spectral shifting on speech perception can be overcome with training. This study simulates bilateral stimulation with a unilateral spectral shift to investigate whether listeners can adapt to upward-shifted speech information presented together with contralateral unshifted information. A six-channel, dichotic, interleaved sine-carrier vocoder simulated a binaurally mismatched frequency-to-place map. Odd channels were presented to one ear with an upward frequency shift equivalent to 6 mm on the basilar membrane, while even channels were presented to the contralateral ear unshifted. In Experiment 1, listeners were trained for 5.3 h with either the binaurally mismatched processor or with just the shifted monaural bands. In Experiment 2, the duration of training was 10 h, and the trained condition alternated between those of Experiment 1. While listeners showed learning in both experiments, intelligibility with the binaurally mismatched processor never exceeded, intelligibility with just the three unshifted bands, suggesting that listeners did not benefit from combining the mismatched maps, even though there was clear scope to do so. Frequency-place map alignment may thus be of importance when optimizing bilateral devices of the type studied here.

Melodic contour identification and music perception by cochlear implant users

Research and outcomes with cochlear implants (CIs) have revealed a dichotomy in the cues necessary for speech and music recognition. CI devices typically transmit 16-22 spectral channels, each modulated slowly in time. This coarse representation provides enough information to support speech understanding in quiet and rhythmic perception in music, but not enough to support speech understanding in noise or melody recognition. Melody recognition requires some capacity for complex pitch perception, which in turn depends strongly on access to spectral fine structure cues. Thus, temporal envelope cues are adequate for speech perception under optimal listening conditions, while spectral fine structure cues are needed for music perception. In this paper, we present recent experiments that directly measure CI users' melodic pitch perception using a melodic contour identification (MCI) task. While normal-hearing (NH) listeners' performance was consistently high across experiments, MCI performance was highly variable across CI users. CI users' MCI performance was significantly affected by instrument timbre, as well as by the presence of a competing instrument. In general, CI users had great difficulty extracting melodic pitch from complex stimuli. However, musically experienced CI users often performed as well as NH listeners, and MCI training in less-experienced subjects greatly improved performance. With fixed constraints on spectral resolution, such as occurs with hearing loss or an auditory prosthesis, training and experience can provide considerable improvements in music perception and appreciation.

Multiple routes to the perceptual learning of speech

A listener's ability to utilize indexical information in the speech signal can enhance their performance on a variety of speech perception tasks. It is unclear, however, whether such information plays a similar role for spectrally reduced speech signals, such as those experienced by individuals with cochlear implants. The present study compared the effects of training on linguistic and indexical tasks when adapting to cochlear implant simulations. Listening to sentences processed with an eight-channel sinewave vocoder, three separate groups of subjects were trained on a transcription task (transcription), a talker identification task (talker ID), or a gender identification task (gender ID). Pre- to posttest comparisons demonstrated that training produced significant improvement for all groups. Moreover, subjects from the talker ID and transcription training groups performed similarly at posttest and generalization, and significantly better than the subjects from the gender ID training group. These results suggest that training on an indexical task that requires high levels of controlled attention can provide equivalent benefits to training on a linguistic task. When listeners selectively focus their attention on the extralinguistic information in the speech signal, they still extract linguistic information, the degree to which they do so, however, appears to be task dependent.

Comparison of word-, sentence-, and phoneme-based training strategies in improving the perception of spectrally distorted speech

PURPOSE

To compare the effectiveness of 3 self-administered strategies for auditory training that might improve speech perception by adult users of cochlear implants. The strategies are based, respectively, on discriminating isolated words, words in sentences, and phonemes in nonsense syllables.

METHOD

Participants were 18 normal-hearing adults who listened to speech processed by a noise-excited vocoder to simulate the information provided by a cochlear implant. They were assigned randomly to word-, sentence-, or phoneme-based training and underwent 9 training sessions (20 min each) on separate days over a 2- to 3-week period. The effectiveness of training was assessed as the improvement in accuracy of discriminating vowels and consonants, as well as identifying words in sentences, relative to participants' best performance in repeated tests prior to training.

RESULTS

Word- and sentence-based training led to significant improvements in the ability to identify words in sentences that were significantly larger than the improvements produced by phoneme-based training. There were no significant differences between the effectiveness of word- and sentence-based training. No significant improvements in consonant or vowel discrimination were found for the sentence- or phoneme-based training groups, but some improvements were found for the word-based training group.

CONCLUSION

The word- and sentence-based training strategies were more effective than the phoneme-based strategy at improving the perception of spectrally distorted speech.

Perceptual learning of spectrally degraded speech and environmental sounds

Adaptation to the acoustic world following cochlear implantation does not typically include formal training or extensive audiological rehabilitation. Can cochlear implant (CI) users benefit from formal training, and if so, what type of training is best? This study used a pre-/posttest design to evaluate the efficacy of training and generalization of perceptual learning in normal hearing subjects listening to CI simulations (eight-channel sinewave vocoder). Five groups of subjects were trained on words (simple/complex), sentences (meaningful/anomalous), or environmental sounds, and then were tested using an open-set identification task. Subjects were trained on only one set of materials but were tested on all stimuli. All groups showed significant improvement due to training, which successfully generalized to some, but not all stimulus materials. For easier tasks, all types of training generalized equally well. For more difficult tasks, training specificity was observed. Training on speech did not generalize to the recognition of environmental sounds; however, explicit training on environmental sounds successfully generalized to speech. These data demonstrate that the perceptual learning of degraded speech is highly context dependent and the type of training and the specific stimulus materials that a subject experiences during perceptual learning has a substantial impact on generalization to new materials.

Perceptual learning and auditory training in cochlear implant recipients

Learning electrically stimulated speech patterns can be a new and difficult experience for cochlear implant (CI) recipients. Recent studies have shown that most implant recipients at least partially adapt to these new patterns via passive, daily-listening experiences. Gradually introducing a speech processor parameter (eg, the degree of spectral mismatch) may provide for more complete and less stressful adaptation. Although the implant device restores hearing sensation and the continued use of the implant provides some degree of adaptation, active auditory rehabilitation may be necessary to maximize the benefit of implantation for CI recipients. Currently, there are scant resources for auditory rehabilitation for adult, postlingually deafened CI recipients. We recently developed a computer-assisted speech-training program to provide the means to conduct auditory rehabilitation at home. The training software targets important acoustic contrasts among speech stimuli, provides auditory and visual feedback, and incorporates progressive training techniques, thereby maintaining recipients' interest during the auditory training exercises. Our recent studies demonstrate the effectiveness of targeted auditory training in improving CI recipients' speech and music perception. Provided with an inexpensive and effective auditory training program, CI recipients may find the motivation and momentum to get the most from the implant device.

Technologic advances in aural rehabilitation: applications and innovative methods of service delivery

The level of interest in aural rehabilitation has increased recently, both in clinical use and in research presentations and publications. Advances in aural rehabilitation have seen previous techniques such as speech tracking and analytic auditory training reappear in computerized forms. These new delivery methods allow for a consistent, cost-effective, and convenient training program. Several computerized aural rehabilitation programs for hearing aid wearers and cochlear implant recipients have recently been developed and were reported on at the 2006 State of the Science Conference of the Rehabilitation Engineering Research Center on Hearing Enhancement at Gallaudet University. This article reviews these programs and outlines the similarities and differences in their design. Another promising area of aural rehabilitation research is the use of pharmaceuticals in the rehabilitation process. The results from a study of the effect of d-amphetamine in conjunction with intensive aural rehabilitation with cochlear implant patients are also described.

Melodic contour identification by cochlear implant listeners

OBJECTIVE

While the cochlear implant provides many deaf patients with good speech understanding in quiet, music perception and appreciation with the cochlear implant remains a major challenge for most cochlear implant users. The present study investigated whether a closed-set melodic contour identification (MCI) task could be used to quantify cochlear implant users' ability to recognize musical melodies and whether MCI performance could be improved with moderate auditory training. The present study also compared MCI performance with familiar melody identification (FMI) performance, with and without MCI training.

METHODS

For the MCI task, test stimuli were melodic contours composed of 5 notes of equal duration whose frequencies corresponded to musical intervals. The interval between successive notes in each contour was varied between 1 and 5 semitones; the "root note" of the contours was also varied (A3, A4, and A5). Nine distinct musical patterns were generated for each interval and root note condition, resulting in a total of 135 musical contours. The identification of these melodic contours was measured in 11 cochlear implant users. FMI was also evaluated in the same subjects; recognition of 12 familiar melodies was tested with and without rhythm cues. MCI was also trained in 6 subjects, using custom software and melodic contours presented in a different frequency range from that used for testing.

RESULTS

Results showed that MCI recognition performance was highly variable among cochlear implant users, ranging from 14% to 91% correct. For most subjects, MCI performance improved as the number of semitones between successive notes was increased; performance was slightly lower for the A3 root note condition. Mean FMI performance was 58% correct when rhythm cues were preserved and 29% correct when rhythm cues were removed. Statistical analyses revealed no significant correlation between MCI performance and FMI performance (with or without rhythmic cues). However, MCI performance was significantly correlated with vowel recognition performance; FMI performance was not correlated with cochlear implant subjects' phoneme recognition performance. Preliminary results also showed that the MCI training improved all subjects' MCI performance; the improved MCI performance also generalized to improved FMI performance.

CONCLUSIONS

Preliminary data indicate that the closed-set MCI task is a viable approach toward quantifying an important component of cochlear implant users' music perception. The improvement in MCI performance and generalization to FMI performance with training suggests that MCI training may be useful for improving cochlear implant users' music perception and appreciation; such training may be necessary to properly evaluate patient performance, as acute measures may underestimate the amount of musical information transmitted by the cochlear implant device and received by cochlear implant listeners.

Effect of training rate on recognition of spectrally shifted speech

OBJECTIVE

Previous studies have shown that the protocol used for auditory training may significantly affect the outcome of training. However, it is unclear how often training should be performed to maximize its benefit. The present study investigated how the frequency of training contributed to normal-hearing listeners' adaptation to spectrally shifted speech.

METHODS

Eighteen normal-hearing listeners were trained with spectrally shifted and compressed speech via an 8-channel acoustic simulation of cochlear implant speech processing. Five short training sessions (1 hr per session) were completed by each subject; subjects were trained at one of three training rates: five sessions per week, three sessions per week, or one session per week. Subjects were trained to identify medial vowels presented in a cVc format; depending on the level of difficulty, the number of response choices was increased and/or the acoustic differences between vowels were reduced. Vowel and consonant recognition was measured before and after training as well as at regular intervals during the training period. Sentence recognition was measured before and after training only.

RESULTS

Results showed that pretraining vowel recognition scores were poor (14.0% correct, on average) for all subjects, due to the severe spectral shift. After five sessions of targeted vowel contrast training, there was a significant improvement of shifted vowel recognition for most subjects. The mean improvement was comparable (approximately 15 percentage points) across the three training rate conditions, despite significant intersubject variability in pre- and pretraining baseline performance. There was no significant difference in training outcomes among the three training rates. Spectrally shifted consonant and sentence recognition also improved by approximately 20 percentage points after training, even though consonants and sentences were not explicitly trained. Similar to vowel recognition, there was no significant difference in training outcomes among the three training rates for shifted consonant and sentence recognition.

CONCLUSIONS

The results demonstrated that the training rate had little effect on normal-hearing listeners' adaptation to spectrally shifted speech, at least for the training periods (ranging from 1 to 5 wk) used in the present study. The outcome of auditory training may depend more strongly on the amount of training (i.e., total number of training sessions) rather than the frequency of training (i.e., daily or once per week). Although more frequent training may accelerate listeners' adaptation to spectrally shifted speech, there may be significant benefits from training as little as one session per week. The results of the present study suggest that appropriate training schedules can be developed to optimize the effectiveness, efficiency, and effort associated with hearing-impaired patients' auditory rehabilitation.

Effectiveness of computer-based auditory training in improving the perception of noise-vocoded speech

Five experiments were designed to evaluate the effectiveness of "high-variability" lexical training in improving the ability of normal-hearing subjects to perceive noise-vocoded speech that had been spectrally shifted to simulate tonotopic misalignment. Two approaches to training were implemented. One training approach required subjects to recognize isolated words, while the other training approach required subjects to recognize words in sentences. Both approaches to training improved the ability to identify words in sentences. Improvements following a single session (lasting 1-2 h) of auditory training ranged between 7 and 12 %pts and were significantly larger than improvements following a visual control task that was matched with the auditory training task in terms of the response demands. An additional three sessions of word- and sentence-based training led to further improvements, with the average overall improvement ranging from 13 to 18% pts. When a tonotopic misalignment of 3 mm rather than 6 mm was simulated, training with several talkers led to greater generalization to new talkers than training with a single talker. The results confirm that computer-based lexical training can help overcome the effects of spectral distortions in speech, and they suggest that training materials are most effective when several talkers are included.

Estimation of Vowel Recognition With Cochlear Implant Simulations

Because there are many parameters in the cochlear implant (CI) device that can be optimized for individual patients, it is important to estimate a parameter's effect before patient evaluation. In this paper, Mel-frequency cepstrum coefficients (MFCCs) were used to estimate the acoustic vowel space for vowel stimuli processed by the CI simulations. The acoustic space was then compared to vowel recognition performance by normal-hearing subjects listening to the same processed speech. Five CI speech processor parameters were simulated to produce different degree of spectral resolution, spectral smearing, spectral warping, spectral shifting, and amplitude distortion. The acoustic vowel space was highly correlated with normal hearing subjects' vowel recognition performance for parameters that affected the spectral channels and spectral smearing. However, the acoustic vowel space was not significantly correlated with perceptual performance for parameters that affected the degree of spectral warping, spectral shifting, and amplitude distortion. In particular, while spectral warping and shifting did not significantly reshape the acoustic space, vowel recognition performance was significantly affected by these parameters. The results from the acoustic analysis suggest that the CI device can preserve phonetic distinctions under conditions of spectral warping and shifting. Auditory training may help CI patients better perceive these speech cues transmitted by their speech processors.