Reception of Environmental Sounds Through Cochlear Implants

Development of Environmental Sound Perception in Children with Cochlear Implant within 4 Months of Implantation

Aim

The aim of the study was (1) to investigate the development of identification of environmental sounds in children with Cochlear Implantation (CI) within four months from switch on (i.e. at 0, 2 and 4 months) and (2) to see the effect of family type in the perception of environmental sounds.

Materials and methods

A longitudinal study design was utilized on a total of 18 children using CI within the chronological age range of 3 to 7 years. All participants underwent a closed set test of Environmental Sound Perception (ESP) to measure the longitudinal outcomes of ESP, at 0 (within 1 week of switch on), 2 months and 4 months of implant age. They were asked to identify the sounds by pointing at the picture representing the sound.

Results

Results using One-way and Two-way ANOVA demonstrated that at 0 month of implant age, the scores were 0%. At 2 months of implant age the scores ranged from 0 to 25% and at 4th month the scores ranged from 0 to 40%. There was a statistically significant improvement observed in ESP at every 2 months of testing from 0 to 4 months of implant age. However, effect of family type revealed no significant differences between the performances across the implant age.

Conclusion

The current study reveals that identification of environmental sounds are one of the foremost benefits and early outcomes of CI in children. The perception of environmental sounds are constantly but gradually developing with increasing implant age. This information is useful to predict the performance of CI during rehabilitation and to set the therapy goals accordingly.

Standardization of Three Familiar Sound Recognition Tests in Hearing and Deaf Adult Populations

OBJECTIVE

Recognition of familiar noises is crucial for understanding and reacting appropriately to our auditory environment. Its improvement is one of the benefits expected after cochlear implantation. The aim of this study was to standardize three environmental sounds noise recognition tests and to illustrate their application to a population of deaf adults with cochlear implants.

METHOD

Norms were established on a sample of 126 normal-hearing adults divided into 6 age groups. Three familiar sound recognition tests were used: 1) the Blue Mouse "First Familiar Sounds" (BM), 2) the UCL-IRSA test (TI), and 3) the Bernadette Piérart Familiar Sounds Test (TBF). These tests were also administered to 61 implanted deaf ears.

RESULTS

We observed a significant effect of age on the accuracy scores of the TI and TBF tests for the hearing group and on the time scores of the TI and BM tests. Overall, the performance of the deaf participants was poorer and more variable than that of the hearing participants.

CONCLUSION

We have three tests that can be used in practice to measure the performance of deaf people (with cochlear implants) at different stages of their pre- and post-implant rehabilitation.

The Optimal Speech-to-Background Ratio for Balancing Speech Recognition With Environmental Sound Recognition

OBJECTIVES

This study aimed to determine the speech-to-background ratios (SBRs) at which normal-hearing (NH) and hearing-impaired (HI) listeners can recognize both speech and environmental sounds when the two types of signals are mixed. Also examined were the effect of individual sounds on speech recognition and environmental sound recognition (ESR), and the impact of divided versus selective attention on these tasks.

DESIGN

In Experiment 1 (divided attention), 11 NH and 10 HI listeners heard sentences mixed with environmental sounds at various SBRs and performed speech recognition and ESR tasks concurrently in each trial. In Experiment 2 (selective attention), 20 NH listeners performed these tasks in separate trials. Psychometric functions were generated for each task, listener group, and environmental sound. The range over which speech recognition and ESR were both high was determined, as was the optimal SBR for balancing recognition with ESR, defined as the point of intersection between each pair of normalized psychometric functions.

RESULTS

The NH listeners achieved greater than 95% accuracy on concurrent speech recognition and ESR over an SBR range of approximately 20 dB or greater. The optimal SBR for maximizing both speech recognition and ESR for NH listeners was approximately +12 dB. For the HI listeners, the range over which 95% performance was observed on both tasks was far smaller (span of 1 dB), with an optimal value of +5 dB. Acoustic analyses indicated that the speech and environmental sound stimuli were similarly audible, regardless of the hearing status of the listener, but that the speech fluctuated more than the environmental sounds. Divided versus selective attention conditions produced differences in performance that were statistically significant yet only modest in magnitude. In all conditions and for both listener groups, recognition was higher for environmental sounds than for speech when presented at equal intensities (i.e., 0 dB SBR), indicating that the environmental sounds were more effective maskers of speech than the converse. Each of the 25 environmental sounds used in this study (with one exception) had a span of SBRs over which speech recognition and ESR were both higher than 95%. These ranges tended to overlap substantially.

CONCLUSIONS

A range of SBRs exists over which speech and environmental sounds can be simultaneously recognized with high accuracy by NH and HI listeners, but this range is larger for NH listeners. The single optimal SBR for jointly maximizing speech recognition and ESR also differs between NH and HI listeners. The greater masking effectiveness of the environmental sounds relative to the speech may be related to the lower degree of fluctuation present in the environmental sounds as well as possibly task differences between speech recognition and ESR (open versus closed set). The observed differences between the NH and HI results may possibly be related to the HI listeners' smaller fluctuating masker benefit. As noise-reduction systems become increasingly effective, the current results could potentially guide the design of future systems that provide listeners with highly intelligible speech without depriving them of access to important environmental sounds.

The future of sensory substitution, addition, and expansion via haptic devices

Haptic devices use the sense of touch to transmit information to the nervous system. As an example, a sound-to-touch device processes auditory information and sends it to the brain via patterns of vibration on the skin for people who have lost hearing. We here summarize the current directions of such research and draw upon examples in industry and academia. Such devices can be used for sensory substitution (replacing a lost sense, such as hearing or vision), sensory expansion (widening an existing sensory experience, such as detecting electromagnetic radiation outside the visible light spectrum), and sensory addition (providing a novel sense, such as magnetoreception). We review the relevant literature, the current status, and possible directions for the future of sensory manipulation using non-invasive haptic devices.

Perception of Environmental Sounds in Cochlear Implant Users: A Systematic Review

Objectives: Improved perception of environmental sounds (PES) is one of the primary benefits of cochlear implantation (CI). However, past research contains mixed findings on PES ability in contemporary CI users, which at times contrast with anecdotal clinical reports. The present review examined extant PES research to provide an evidence basis for clinical counseling, identify knowledge gaps, and suggest directions for future work in this area of CI outcome assessment.

Methods: Six electronic databases were searched using medical subject headings (MeSH) and keywords broadly identified to reference CI and environmental sounds. Records published between 2000 and 2021 were screened by two independent reviewers in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement to identify studies that met the inclusion criteria. Data were subsequently extracted and evaluated according to synthesis without-meta-analysis (SWiM) guidelines.

Results: Nineteen studies met the inclusion criteria. Most examined PES in post-lingually implanted adults, with one study focused on pre/perilingual adults. Environmental sound identification (ESI) in quiet using open- or closed-set response format was most commonly used in PES assessment, included in all selected studies. ESI accuracy in CI children (3 studies) and adults (16 studies), was highly variable but generally mediocre (means range: 31–87%). Only two studies evaluated ESI performance prospectively before and after CI, while most studies were cross-sectional. Overall, CI performance was consistently lower than that of normal-hearing peers. No significant differences in identification accuracy were reported between CI candidates and CI users. Environmental sound identification correlated in CI users with measures of speech perception, music and spectro-temporal processing.

Conclusion: The findings of this systematic review indicate considerable limitations in the current knowledge of PES in contemporary CI users, especially in pre/perilingual late-implanted adults and children. Although no overall improvement in PES following implantation was found, large individual variability and existing methodological limitations in PES assessment may potentially obscure potential CI benefits for PES. Further research in this ecologically relevant area of assessment is needed to establish a stronger evidence basis, identify CI users with significant deficits, and improve CI users' safety and satisfaction through targeted PES rehabilitation.

The Influence of the Type of Background Noise on Perceptual Learning of Speech in Noise

OBJECTIVES

Auditory perceptual learning studies tend to focus on the nature of the target stimuli. However, features of the background noise can also have a significant impact on the amount of benefit that participants obtain from training. This study explores whether perceptual learning of speech in background babble noise generalizes to other, real-life environmental background noises (car and rain), and if the benefits are sustained over time.

DESIGN

Normal-hearing native English speakers were randomly assigned to a training (n = 12) or control group (n = 12). Both groups completed a pre- and post-test session in which they identified Bamford-Kowal-Bench (BKB) target words in babble, car, or rain noise. The training group completed speech-in-babble noise training on three consecutive days between the pre- and post-tests. A follow up session was conducted between 8 and 18 weeks after the post-test session (training group: n = 9; control group: n = 7).

RESULTS

Participants who received training had significantly higher post-test word identification accuracy than control participants for all three types of noise, although benefits were greatest for the babble noise condition and weaker for the car- and rain-noise conditions. Both training and control groups maintained their pre- to post-test improvement over a period of several weeks for speech in babble noise, but returned to pre-test accuracy for speech in car and rain noise.

CONCLUSION

The findings show that training benefits can show some generalization from speech-in-babble noise to speech in other types of environmental noise. Both groups sustained their learning over a period of several weeks for speech-in-babble noise. As the control group received equal exposure to all three noise types, the sustained learning with babble noise, but not other noises, implies that a structural feature of babble noise was conducive to the sustained improvement. These findings emphasize the importance of considering the background noise as well as the target stimuli in auditory perceptual learning studies.

A Longitudinal Comparison of Environmental Sound Recognition in Adults With Hearing Aids Before and After Cochlear Implantation

Purpose The aims of this study were (a) to longitudinally assess environmental sound recognition (ESR) before and after cochlear implantation in a sample of postlingually deafened adults and (b) to assess the extent to which spectro-temporal processing abilities influence ESR with cochlear implants (CIs). Method In a longitudinal cohort study, 20 postlingually deafened adults were tested with hearing aids on the Familiar Environmental Sound Test-Identification and AzBio sentences in quiet pre-CI and 6 months post-CI. A subset of 11 participants were also tested 12 months post-CI. Pre-CI spectro-temporal processing was assessed using the Spectral-temporally Modulated Ripple Test. Results Average ESR accuracy pre-CI (M = 63.60%) was not significantly different from ESR accuracy at 6 months (M = 65.40%) or 12 months (M = 69.09%) post-CI. In 11 participants (55%), however, ESR improved following implantation by 10.91 percentage points, on average. Pre-CI ESR correlated moderately and significantly with pre-CI and 12-month post-CI AzBio scores, with a trend toward significance for AzBio performance at 6 months. Pre-CI spectro-temporal processing was moderately associated with ESR at 6 and 12 months post-CI but not with speech recognition post-CI. Conclusions The present findings failed to demonstrate an overall significant improvement in ESR following implantation. Nevertheless, more than half of our sample showed some degree of improvement in ESR. Several environmental sounds were poorly identified both before and after implantation. Spectro-temporal processing ability prior to implantation appears to predict postimplantation performance for ESR. These findings indicate the need for greater attention to ESR following cochlear implantation and for developing individualized targets for ESR rehabilitation. Supplemental Material https://doi.org/10.23641/asha.13876745.

Deciphering Sounds Through Patterns of Vibration on the Skin

Sensory substitution refers to the concept of feeding information to the brain via an atypical sensory pathway. We here examined the degree to which participants (deaf and hard of hearing) can learn to identify sounds that are algorithmically translated into spatiotemporal patterns of vibration on the skin of the wrist. In a three-alternative forced choice task, participants could determine the identity of up to 95% and on average 70% of the stimuli simply by the spatial pattern of vibrations on the skin. Performance improved significantly over the course of 1 month. Younger participants tended to score better, possibly because of higher brain plasticity, more sensitive skin, or better skills at playing digital games. Similar results were obtained with pattern discrimination, in which a pattern representing the sound of one word was presented to the skin, followed by that of a second word. Participants answered whether the word was the same or different. With minimal difference pairs (distinguished by only one phoneme, such as "house" and "mouse"), the best performance was 83% (average of 62%), while with non-minimal pairs (such as "house" and "zip") the best performance was 100% (average of 70%). Collectively, these results demonstrate that participants are capable of using the channel of the skin to interpret auditory stimuli, opening the way for low-cost, wearable sensory substitution for the deaf and hard of hearing communities.

An evaluation framework for research platforms to advance cochlear implant/hearing aid technology: A case study with CCi-MOBILE

Cochlear implants (CIs) and hearing aids (HAs) are advanced assistive hearing devices that perform sound processing to achieve acoustic to acoustic/electrical stimulation, thus enabling the prospects for hearing restoration and rehabilitation. Since commercial CIs/HAs are typically constrained by manufacturer design/production constraints, it is necessary for researchers to use research platforms (RPs) to advance algorithms and conduct investigational studies with CI/HA subjects. While previous CI/HA research platforms exist, no study has explored establishing a formal evaluation protocol for the operational safety and reliability of RPs. This study proposes a two-phase analysis and evaluation paradigm for RPs. In the acoustic phase 1 step, a signal processing acoustic space is explored in order to present a sampled set of audio input content to explore the safety of the resulting output electric/acoustic stimulation. In the parameter phase 2 step, the configurable space for realizable electrical stimulation pulses is determined, and overall stimulation reliability and safety are evaluated. The proposed protocol is applied and demonstrated using Costakis Cochlear Implant Mobile. Assessment protocol observations, results, and additional best practices for subsampling of the acoustic and parameter test spaces are discussed. The proposed analysis-evaluation protocol establishes a viable framework for assessing RP operational safety and reliability. Guidelines for adapting the proposed protocol to address variability in RP configuration due to experimental factors such as custom algorithms, stimulation techniques, and/or individualization are also considered.

Sound therapy for cochlear implant users with tinnitus

OBJECTIVE

Despite the positive effect of a cochlear implant (CI) on tinnitus in many patients, tinnitus remains a problem for a significant proportion of CI users. We investigated the acceptability and effect of sound therapy (a combination of natural background sounds and one concise tinnitus counselling session) on tinnitus and speech perception in CI users who still experienced tinnitus during CI use.

DESIGN AND STUDY SAMPLE

Thirty-two CI users (32-78 years) participated in phase 1: a test at the clinic to evaluate six background sounds provided by the sound processor. Eighteen out of the 32 CI users participated in phase 2: an optional take-home evaluation of 2 weeks without sound therapy, followed by 5 weeks with sound therapy, ending with an evaluation visit.

RESULTS

Thirty subjects (93.8%) found at least one background sound acceptable. In phase 2, a small improvement with sound therapy was found for tinnitus loudness, annoyance, and intrusiveness. 50% of the subjects subjectively reported benefit of sound therapy. Especially the sense of control on their tinnitus was highly appreciated. No detrimental effect on speech perception was observed.

CONCLUSION

The background sounds were acceptable and provided tinnitus relief in some CI users with tinnitus during CI use.

Development of the Basic Auditory Skills Evaluation Battery for Online Testing of Cochlear Implant Listeners

Purpose Cochlear implant (CI) performance varies considerably across individuals and across domains of auditory function, but clinical testing is typically restricted to speech intelligibility. The goals of this study were (a) to develop a basic auditory skills evaluation battery of tests for comprehensive assessment of ecologically relevant aspects of auditory perception and (b) to compare CI listeners' performance on the battery when tested in the laboratory by an audiologist or independently at home. Method The battery included 17 tests to evaluate (a) basic spectrotemporal processing, (b) processing of music and environmental sounds, and (c) speech perception in both quiet and background noise. The battery was administered online to three groups of adult listeners: two groups of postlingual CI listeners and a group of older normal-hearing (ONH) listeners of similar age. The ONH group and one CI group were tested in a laboratory by an audiologist, whereas the other CI group self-tested independently at home following online instructions. Results Results indicated a wide range in the performance of CI but not ONH listeners. Significant differences were not found between the two CI groups on any test, whereas on all but two tests, CI listeners' performance was lower than that of the ONH participants. Principal component analysis revealed that four components accounted for 82% of the variance in measured results, with component loading indicating that the test battery successfully captures differences across dimensions of auditory perception. Conclusions These results provide initial support for the use of the basic auditory skills evaluation battery for comprehensive online assessment of auditory skills in adult CI listeners.

Are There Real-world Benefits to Bimodal Listening?

OBJECTIVE

To assess the benefits of bimodal listening (i.e., addition of contralateral hearing aid) for cochlear implant (CI) users on real-world tasks involving high-talker variability speech materials, environmental sounds, and self-reported quality of life (quality of hearing) in listeners' own best-aided conditions.

STUDY DESIGN

Cross-sectional study between groups.

SETTING

Outpatient hearing clinic.

PATIENTS

Fifty experienced adult CI users divided into groups based on normal daily listening conditions (i.e., best-aided conditions): unilateral CI (CI), unilateral CI with contralateral HA (bimodal listening; CIHA), or bilateral CI (CICI).

INTERVENTION

Task-specific measures of speech recognition with low (Harvard Standard Sentences) and high (Perceptually Robust English Sentence Test Open-set corpus) talker variability, environmental sound recognition (Familiar Environmental Sounds Test-Identification), and hearing-related quality of life (Nijmegen Cochlear Implant Questionnaire).

MAIN OUTCOME MEASURES

Test group differences among CI, CIHA, and CICI conditions.

RESULTS

No group effect was observed for speech recognition with low or high-talker variability, or hearing-related quality of life. Bimodal listeners demonstrated a benefit in environmental sound recognition compared with unilateral CI listeners, with a trend of greater benefit than the bilateral CI group. There was also a visual trend for benefit on high-talker variability speech recognition.

CONCLUSIONS

Findings provide evidence that bimodal listeners demonstrate stronger environmental sound recognition compared with unilateral CI listeners, and support the idea that there are additional advantages to bimodal listening after implantation other than speech recognition measures, which are at risk of being lost if considering bilateral implantation.

Categorization of everyday sounds by cochlear implanted children

Auditory categorization is an important process in the perception and understanding of everyday sounds. The use of cochlear implants (CIs) may affect auditory categorization and result in poor abilities. The current study was designed to compare how children with normal hearing (NH) and children with CIs categorize a set of everyday sounds. We tested 24 NH children and 24 children with CI on a free-sorting task of 18 everyday sounds corresponding to four a priori categories: nonlinguistic human vocalizations, environmental sounds, musical sounds, and animal vocalizations. Multiple correspondence analysis revealed considerable variation within both groups of child listeners, although the human vocalizations and musical sounds were similarly categorized. In contrast to NH children, children with CIs categorized some sounds according to their acoustic content rather than their associated semantic information. These results show that despite identification deficits, children with CIs are able to categorize environmental and vocal sounds in a similar way to NH children, and are able to use categorization as an adaptive process when dealing with everyday sounds.

Frequency-Limiting Effects on Speech and Environmental Sound Identification for Cochlear Implant and Normal Hearing Listeners

BACKGROUND AND OBJECTIVES

It is important to understand the frequency region of cues used, and not used, by cochlear implant (CI) recipients. Speech and environmental sound recognition by individuals with CI and normal-hearing (NH) was measured. Gradients were also computed to evaluate the pattern of change in identification performance with respect to the low-pass filtering or high-pass filtering cutoff frequencies.

SUBJECTS AND METHODS

Frequency-limiting effects were implemented in the acoustic waveforms by passing the signals through low-pass filters (LPFs) or high-pass filters (HPFs) with seven different cutoff frequencies. Identification of Korean vowels and consonants produced by a male and female speaker and environmental sounds was measured. Crossover frequencies were determined for each identification test, where the LPF and HPF conditions show the identical identification scores.

RESULTS

CI and NH subjects showed changes in identification performance in a similar manner as a function of cutoff frequency for the LPF and HPF conditions, suggesting that the degraded spectral information in the acoustic signals may similarly constraint the identification performance for both subject groups. However, CI subjects were generally less efficient than NH subjects in using the limited spectral information for speech and environmental sound identification due to the inefficient coding of acoustic cues through the CI sound processors.

CONCLUSIONS

This finding will provide vital information in Korean for understanding how different the frequency information is in receiving speech and environmental sounds by CI processor from normal hearing.

The Relationship Between Environmental Sound Awareness and Speech Recognition Skills in Experienced Cochlear Implant Users

HYPOTHESIS

1) Environmental sound awareness (ESA) and speech recognition skills in experienced, adult cochlear implant (CI) users will be highly correlated, and, 2) ESA skills of CI users will be significantly lower than those of age-matched adults with normal hearing.

BACKGROUND

Enhancement of ESA is often discussed with patients with sensorineural hearing loss as a potential benefit of implantation and, in some cases, ESA may be a major motivating factor. Despite its ecological validity and patients' expectations, ESA remains largely a presumed skill. The relationship between ESA and speech recognition is not well-understood.

METHODS

ESA was assessed in 35 postlingually deaf, experienced CI users and a control group of 41 age-matched, normal hearing listeners using the validated, computerized familiar environmental sounds test-identification (FEST-I) and a diverse speech recognition battery. Demographic and audiological factors as well as nonverbal intelligence quotient (IQ)/nonverbal reasoning and spectral resolution were assessed.

RESULTS

Six of the 35 experienced CI users (17%) demonstrated FEST-I accuracy within the range of the NH controls. Among CI users all correlations between FEST-I accuracy and speech recognition scores were strong. Chronological age at the time of testing, duration of deafness, spectral resolution, and nonverbal IQ/nonverbal reasoning were strongly correlated with FEST-I accuracy. Partial correlation analysis showed that correlations between FEST-I and speech recognition measures remained significant when controlling for the demographic and audiological factors.

CONCLUSION

Our findings reinforce the hypothesis that ESA and speech perception share common underlying processes rather than reflecting truly separate auditory domains.

Toward a Nonspeech Test of Auditory Cognition: Semantic Context Effects in Environmental Sound Identification in Adults of Varying Age and Hearing Abilities

OBJECTIVE

Sounds in everyday environments tend to follow one another as events unfold over time. The tacit knowledge of contextual relationships among environmental sounds can influence their perception. We examined the effect of semantic context on the identification of sequences of environmental sounds by adults of varying age and hearing abilities, with an aim to develop a nonspeech test of auditory cognition.

METHOD

The familiar environmental sound test (FEST) consisted of 25 individual sounds arranged into ten five-sound sequences: five contextually coherent and five incoherent. After hearing each sequence, listeners identified each sound and arranged them in the presentation order. FEST was administered to young normal-hearing, middle-to-older normal-hearing, and middle-to-older hearing-impaired adults (Experiment 1), and to postlingual cochlear-implant users and young normal-hearing adults tested through vocoder-simulated implants (Experiment 2).

RESULTS

FEST scores revealed a strong positive effect of semantic context in all listener groups, with young normal-hearing listeners outperforming other groups. FEST scores also correlated with other measures of cognitive ability, and for CI users, with the intelligibility of speech-in-noise.

CONCLUSIONS

Being sensitive to semantic context effects, FEST can serve as a nonspeech test of auditory cognition for diverse listener populations to assess and potentially improve everyday listening skills.

Categorization of common sounds by cochlear implanted and normal hearing adults

Auditory categorization involves grouping of acoustic events along one or more shared perceptual dimensions which can relate to both semantic and physical attributes. This process involves both high level cognitive processes (categorization) and low-level perceptual encoding of the acoustic signal, both of which are affected by the use of a cochlear implant (CI) device. The goal of this study was twofold: I) compare the categorization strategies of CI users and normal hearing listeners (NHL) II) investigate if any characteristics of the raw acoustic signal could explain the results. 16 experienced CI users and 20 NHL were tested using a Free-Sorting Task of 16 common sounds divided into 3 predefined categories of environmental, musical and vocal sounds. Multiple Correspondence Analysis (MCA) and Hierarchical Clustering based on Principal Components (HCPC) show that CI users followed a similar categorization strategy to that of NHL and were able to discriminate between the three different types of sounds. However results for CI users were more varied and showed less inter-participant agreement. Acoustic analysis also highlighted the average pitch salience and average autocorrelation peak as being important for the perception and categorization of the sounds. The results therefore show that on a broad level of categorization CI users may not have as many difficulties as previously thought in discriminating certain kinds of sound; however the perception of individual sounds remains challenging.

Environmental sound training in cochlear implant users

PURPOSE

The study investigated the effect of a short computer-based environmental sound training regimen on the perception of environmental sounds and speech in experienced cochlear implant (CI) patients.

METHOD

Fourteen CI patients with the average of 5 years of CI experience participated. The protocol consisted of 2 pretests, 1 week apart, followed by 4 environmental sound training sessions conducted on separate days in 1 week, and concluded with 2 posttest sessions, separated by another week without training. Each testing session included an environmental sound test, which consisted of 40 familiar everyday sounds, each represented by 4 different tokens, as well as the Consonant Nucleus Consonant (CNC) word test, and Revised Speech Perception in Noise (SPIN-R) sentence test.

RESULTS

Environmental sounds scores were lower than for either of the speech tests. Following training, there was a significant average improvement of 15.8 points in environmental sound perception, which persisted 1 week later after training was discontinued. No significant improvements were observed for either speech test.

CONCLUSIONS

The findings demonstrate that environmental sound perception, which remains problematic even for experienced CI patients, can be improved with a home-based computer training regimen. Such computer-based training may thus provide an effective low-cost approach to rehabilitation for CI users, and potentially, other hearing impaired populations.

Reliability measure of a clinical test: Appreciation of Music in Cochlear Implantees (AMICI)

PURPOSE

The goals of this study were (1) to investigate the reliability of a clinical music perception test, Appreciation of Music in Cochlear Implantees (AMICI), and (2) examine associations between the perception of music and speech. AMICI was developed as a clinical instrument for assessing music perception in persons with cochlear implants (CIs). The test consists of four subtests: (1) music versus environmental noise discrimination, (2) musical instrument identification (closed-set), (3) musical style identification (closed-set), and (4) identification of musical pieces (open-set). To be clinically useful, it is crucial for AMICI to demonstrate high test-retest reliability, so that CI users can be assessed and retested after changes in maps or programming strategies.

RESEARCH DESIGN

Thirteen CI subjects were tested with AMICI for the initial visit and retested again 10-14 days later. Two speech perception tests (consonant-nucleus-consonant [CNC] and Bamford-Kowal-Bench Speech-in-Noise [BKB-SIN]) were also administered.

DATA ANALYSIS

Test-retest reliability and equivalence of the test's three forms were analyzed using paired t-tests and correlation coefficients, respectively. Correlation analysis was also conducted between results from the music and speech perception tests.

RESULTS

Results showed no significant difference between test and retest (p > 0.05) with adequate power (0.9) as well as high correlations between the three forms (Forms A and B, r = 0.91; Forms A and C, r = 0.91; Forms B and C, r = 0.95). Correlation analysis showed high correlation between AMICI and BKB-SIN (r = -0.71), and moderate correlation between AMICI and CNC (r = 0.4).

CONCLUSIONS

The study showed AMICI is highly reliable for assessing musical perception in CI users.

Environmental sounds recognition in children with cochlear implants

The aims of this study were (1) to document the recognition performance of environmental sounds (ESs) in Mandarin-speaking children with cochlear implants (CIs) and to analyze the possible associated factors with the ESs recognition; (2) to examine the relationship between perception of ESs and receptive vocabulary level; and (3) to explore the acoustic factors relevant to perceptual outcomes of daily ESs in pediatric CI users. Forty-seven prelingually deafened children between ages 4 to 10 years participated in this study. They were divided into pre-school (group A: age 4–6) and school-age (group B: age 7 to 10) groups. Sound Effects Recognition Test (SERT) and the Chinese version of the revised Peabody Picture Vocabulary Test (PPVT-R) were used to assess the auditory perception ability. The average correct percentage of SERT was 61.2% in the preschool group and 72.3% in the older group. There was no significant difference between the two groups. The ESs recognition performance of children with CIs was poorer than that of their hearing peers (90% in average). No correlation existed between ESs recognition and receptive vocabulary comprehension. Two predictive factors: pre-implantation residual hearing and duration of CI usage were found to be associated with recognition performance of daily-encountered ESs. Acoustically, sounds with distinct temporal patterning were easier to identify for children with CIs. In conclusion, we have demonstrated that ESs recognition is not easy for children with CIs and a low correlation existed between linguistic sounds and ESs recognition in these subjects. Recognition ability of ESs in children with CIs can only be achieved by natural exposure to daily-encountered auditory stimuli if sounds other than speech stimuli were less emphasized in routine verbal/oral habilitation program. Therefore, task-specific measures other than speech materials can be helpful to capture the full profile of auditory perceptual progress after implantation.

Environmental sound perception of cochlear implant users

The purposes of this study were (1) to develop a new test of environmental sound perception, the Environmental Sounds Perception Test (EST), (2) to compare the performance of experienced cochlear implant (CI) recipients with that of age-equivalent normally hearing (NH) listeners using this new test, and (3) to pilot test its clinical use as a pre-to-post assessment tool. The closed-set EST consisted of 45 different sounds classified into 9 categories, with each sound being represented by 2 different tokens. The results showed that the NH participants scored significantly higher than the experienced CI users (p<0.001). For the pre-to-post CI group, higher scores were obtained post-surgery with the CI; this difference was approaching significance (p=0.068). Overall these results suggest that CI recipients perform poorer than NH participants on the EST but better than hearing-aid users with a similar level of hearing loss.

Perception of environmental sounds by experienced cochlear implant patients

OBJECTIVES

Environmental sound perception serves an important ecological function by providing listeners with information about objects and events in their immediate environment. Environmental sounds such as car horns, baby cries, or chirping birds can alert listeners to imminent dangers as well as contribute to one's sense of awareness and well being. Perception of environmental sounds as acoustically and semantically complex stimuli may also involve some factors common to the processing of speech. However, very limited research has investigated the abilities of cochlear implant (CI) patients to identify common environmental sounds, despite patients' general enthusiasm about them. This project (1) investigated the ability of patients with modern-day CIs to perceive environmental sounds, (2) explored associations among speech, environmental sounds, and basic auditory abilities, and (3) examined acoustic factors that might be involved in environmental sound perception.

DESIGN

Seventeen experienced postlingually deafened CI patients participated in the study. Environmental sound perception was assessed with a large-item test composed of 40 sound sources, each represented by four different tokens. The relationship between speech and environmental sound perception and the role of working memory and some basic auditory abilities were examined based on patient performance on a battery of speech tests (HINT, CNC, and individual consonant and vowel tests), tests of basic auditory abilities (audiometric thresholds, gap detection, temporal pattern, and temporal order for tones tests), and a backward digit recall test.

RESULTS

The results indicated substantially reduced ability to identify common environmental sounds in CI patients (45.3%). Except for vowels, all speech test scores significantly correlated with the environmental sound test scores: r = 0.73 for HINT in quiet, r = 0.69 for HINT in noise, r = 0.70 for CNC, r = 0.64 for consonants, and r = 0.48 for vowels. HINT and CNC scores in quiet moderately correlated with the temporal order for tones. However, the correlation between speech and environmental sounds changed little after partialling out the variance due to other variables.

CONCLUSIONS

Present findings indicate that environmental sound identification is difficult for CI patients. They further suggest that speech and environmental sounds may overlap considerably in their perceptual processing. Certain spectrotemproral processing abilities are separately associated with speech and environmental sound performance. However, they do not appear to mediate the relationship between speech and environmental sounds in CI patients. Environmental sound rehabilitation may be beneficial to some patients. Environmental sound testing may have potential diagnostic applications, especially with difficult-to-test populations and might also be predictive of speech performance for prelingually deafened patients with cochlear implants.

Voice discrimination in cochlear-implanted deaf subjects

The human voice is important for social communication because voices carry speech and other information such as a person's physical characteristics and affective state. Further restricted temporal cortical regions are specifically involved in voice processing. In cochlear-implanted deaf patients, the processor alters the spectral cues which are crucial for the perception of the paralinguistic information of human voices. The aim of this study was to assess the abilities of voice discrimination in cochlear-implant (CI) users and in normal-hearing subjects (NHS) using a CI simulation (vocoder). In NHS the performance in voice discrimination decreased when reducing the spectral information by decreasing the number of channels of the vocoder. In CI patients with different delays after implantation we observed a strong impairment in voice discrimination at time of activation of the neuroprosthesis. No significant improvement can be detected in patients after two years of experience of the implant while they have reached a higher level of recovery of speech perception, suggesting a dissociation in the dynamic of functional recuperation of speech and voice processing. In addition to the lack of spectral cues due to the implant processor, we hypothesized that the origin of such deficit could derive from a crossmodal reorganization of the temporal voice areas in CI patients.

Cochlear implant-mediated perception of nonlinguistic sounds

OBJECTIVES

The overwhelming majority of test measures to assess cochlear implant (CI) candidacy, efficacy, and progress are based on speech perception. Nonlinguistic sounds, such as alerting and nonspeech human generated sounds, have received comparatively little attention, despite their central importance for daily living and environmental sound awareness. The purposes of this study were to develop and validate a beta test measure of nonlinguistic sound perception and to assess performance in CI users.

DESIGN

A beta test of nonlinguistic sound perception, referred to as the NonLinguistic Sounds Test (NLST) was developed. The NLST consists of 50 sound tokens distributed over five categories (animal, human nonspeech, mechanical/alerting, nature, and musical instruments). Both closed-set (category identification) and open-set (token identification) nonlinguistic sound perceptions were examined. Twenty-two postlingually deafened CI users (mean age, 59.4 +/- 10 yrs) were evaluated using common speech perception test measures (Hearing In Noise test and Consonant-Nucleus-Consonant words) and the NLST following a pilot study in which nonlinguistic sound tokens used were selected or eliminated.

RESULTS

The NLST was easily administered to all 22 CI subjects. An overall token identification score of 49 +/- 13.5% correct was obtained across all five categories. CI users were able to identify the correct category for 71 +/- 11.5% of tokens. A moderate correlation between speech perception and accuracy of nonlinguistic identification was found (r = 0.519, p = 0.016).

CONCLUSIONS

The results suggest that nonlinguistic sounds are difficult for CI users to perceive. The categorization and identification scores suggest that sounds with harmonic structure or sounds with repetitive temporal structure are easier for CI users to perceive. A further developed clinical version of the NLST may be a useful clinical test to measure CI performance and progress, and perception of nonlinguistic sounds should receive greater attention during postimplant auditory rehabilitation.

Effects of semantic context and feedback on perceptual learning of speech processed through an acoustic simulation of a cochlear implant

The effect of feedback and materials on perceptual learning was examined in listeners with normal hearing who were exposed to cochlear implant simulations. Generalization was most robust when feedback paired the spectrally degraded sentences with their written transcriptions, promoting mapping between the degraded signal and its acoustic-phonetic representation. Transfer-appropriate processing theory suggests that such feedback was most successful because the original learning conditions were reinstated at testing: Performance was facilitated when both training and testing contained degraded stimuli. In addition, the effect of semantic context on generalization was assessed by training listeners on meaningful or anomalous sentences. Training with anomalous sentences was as effective as that with meaningful sentences, suggesting that listeners were encouraged to use acoustic-phonetic information to identify speech than to make predictions from semantic context.

Transfer of auditory perceptual learning with spectrally reduced speech to speech and nonspeech tasks: implications for cochlear implants

OBJECTIVE

The objective of this study was to assess whether training on speech processed with an eight-channel noise vocoder to simulate the output of a cochlear implant would produce transfer of auditory perceptual learning to the recognition of nonspeech environmental sounds, the identification of speaker gender, and the discrimination of talkers by voice.

DESIGN

Twenty-four normal-hearing subjects were trained to transcribe meaningful English sentences processed with a noise vocoder simulation of a cochlear implant. An additional 24 subjects served as an untrained control group and transcribed the same sentences in their unprocessed form. All subjects completed pre- and post-test sessions in which they transcribed vocoded sentences to provide an assessment of training efficacy. Transfer of perceptual learning was assessed using a series of closed set, nonlinguistic tasks: subjects identified talker gender, discriminated the identity of pairs of talkers, and identified ecologically significant environmental sounds from a closed set of alternatives.

RESULTS

Although both groups of subjects showed significant pre- to post-test improvements, subjects who transcribed vocoded sentences during training performed significantly better at post-test than those in the control group. Both groups performed equally well on gender identification and talker discrimination. Subjects who received explicit training on the vocoded sentences, however, performed significantly better on environmental sound identification than the untrained subjects. Moreover, across both groups, pre-test speech performance and, to a higher degree, post-test speech performance, were significantly correlated with environmental sound identification. For both groups, environmental sounds that were characterized as having more salient temporal information were identified more often than environmental sounds that were characterized as having more salient spectral information.

CONCLUSIONS

Listeners trained to identify noise-vocoded sentences showed evidence of transfer of perceptual learning to the identification of environmental sounds. In addition, the correlation between environmental sound identification and sentence transcription indicates that subjects who were better able to use the degraded acoustic information to identify the environmental sounds were also better able to transcribe the linguistic content of novel sentences. Both trained and untrained groups performed equally well ( approximately 75% correct) on the gender-identification task, indicating that training did not have an effect on the ability to identify the gender of talkers. Although better than chance, performance on the talker discrimination task was poor overall ( approximately 55%), suggesting that either explicit training is required to discriminate talkers' voices reliably or that additional information (perhaps spectral in nature) not present in the vocoded speech is required to excel in such tasks. Taken together, the results suggest that although transfer of auditory perceptual learning with spectrally degraded speech does occur, explicit task-specific training may be necessary for tasks that cannot rely on temporal information alone.

Cochlear implants and spoken language processing abilities: review and assessment of the literature

Cochlear implants (CIs) process sounds electronically and then transmit electric stimulation to the cochlea of individuals with sensorineural deafness, restoring some sensation of auditory perception. Many congenitally deaf CI recipients achieve a high degree of accuracy in speech perception and develop near-normal language skills. Post-lingually deafened implant recipients often regain the ability to understand and use spoken language with or without the aid of visual input (i.e. lip reading). However, there is wide variation in individual outcomes following cochlear implantation, and some CI recipients never develop useable speech and oral language skills. The causes of this enormous variation in outcomes are only partly understood at the present time. The variables most strongly associated with language outcomes are age at implantation and mode of communication in rehabilitation. Thus, some of the more important factors determining success of cochlear implantation are broadly related to neural plasticity that appears to be transiently present in deaf individuals. In this article we review the expected outcomes of cochlear implantation, potential predictors of those outcomes, the basic science regarding critical and sensitive periods, and several new research directions in the field of cochlear implantation.

Identification of environmental sounds with varying spectral resolution

OBJECTIVES

This study investigated the identification of familiar environmental sounds with varying spectral resolution to establish (1) the number of frequency channels needed to perceive a large heterogeneous set of familiar environmental sounds, (2) the role of cross-channel asynchrony in identification performance, and (3) the acoustic correlates of the spectral resolution required for identification.

DESIGN

In experiment 1, 60 normal-hearing listeners identified environmental sounds in a 60-alternative closed--set response task as a function of six spectral resolution conditions (i.e., 2, 4, 8, 16, 24, and 32 frequency channels) obtained with an envelope-vocoder. In experiment 2, identification accuracy for varying amounts of cross-channel asynchrony was determined for sounds with preserved and degraded fine spectral structure in 10 normal-hearing listeners. Experiment 3 examined identification performance of 72 listeners across six spectral resolution conditions as in experiment 1, but using three different signal processing methods designed to minimize cross-channel asynchrony across channels. Follow-up acoustic and discriminant analyses were carried out to identify parameters that can distinguish environmental sounds based on required spectral resolution.

RESULTS

Identification accuracy tended to improve with increasing spectral resolution reaching the maximum of 76%. However, in experiment 1, performance did not change significantly beyond eight channels, whereas identification accuracy of some sounds declined with increasing spectral resolution. In experiment 2, increases in cross-channel asynchrony for sounds with preserved fine spectra had a small, but significant negative effect on identification. However, minimizing the amount of asynchrony had no significant effect on the overall identification of spectrally degraded sounds in experiment 3. Acoustic analysis indicated several spectral and temporal measures that differed significantly between sounds that required eight or fewer channels and those that required 16 or more channels for 70% correct identification. Discriminant analysis revealed that the sounds could be classified into high- and low-required spectral resolution groups with 83% accuracy based on only two acoustic parameters: the number of bursts in the envelope and the standard deviation of spectral centroid velocity.

CONCLUSIONS

Increasing spectral resolution generally had a positive effect on identification of familiar environmental sounds. However, across conditions performance accuracy remained well-below that of control stimuli with preserved fine spectra, despite becoming asymptotic above eight channels. Cross-channel asynchrony introduced during vocoder processing, although detrimental for some sounds, was not a major factor that prevented further improvement in overall accuracy. A spectral resolution greater than 32 channels, along with additional fine spectral and temporal information may be required for identification of a number of environmental sounds. This study provides a preliminary basis for optimizing environmental sound perception by cochlear implant users by highlighting the role of several acoustic factors important for environmental sound identification.

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.