Cochlear implant-mediated perception of nonlinguistic sounds

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.

Identification Accuracy of Safety-Relevant Environmental Sounds in Adult Cochlear Implant Users

OBJECTIVE

Examine cochlear implant (CI) users' ability to identify safety-relevant environmental sounds, imperative for safety, independence, and personal well-being.

METHODS

Twenty-one experienced adult CI users completed an Environmental Sound Identification (ESI) test consisting of 42 common environmental sounds, 28 of which were relevant to personal safety, along with 14 control sounds. Prior to sound identification, participants were shown sound names and asked to rate the familiarity and, separately, relevance to safety of each corresponding sound on a 1-5 scale.

RESULTS

Overall ESI accuracy was 57% correct for the safety-relevant sounds and 55% correct for control sounds. Participants rated safety-relevant sounds as more important to safety and more familiar than the non-safety sounds. ESI accuracy significantly correlated with familiarity ratings.

CONCLUSION

The present findings suggest mediocre ESI accuracy in postlingual adult CI users for safety-relevant and other environmental sounds. Deficits in the identification of these sounds may put CI listeners at increased risk of accidents or injuries and may require a specific rehabilitation program to improve CI outcomes.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:2388-2393, 2023.

A convolutional neural network-based framework for analysis and assessment of non-linguistic sound classification and enhancement for normal hearing and cochlear implant listeners

Naturalistic sounds encode salient acoustic content that provides situational context or subject/system properties essential for acoustic awareness, autonomy, safety, and improved quality of life for individuals with sensorineural hearing loss. Cochlear implants (CIs) are an assistive hearing device that restores auditory function in hearing impaired individuals. Most CI research advancements have focused on improving speech recognition in noisy, reverberant, or time-varying diverse environments. Relatively few studies have explored non-linguistic sound (NLS) perception among CIs, and those that have carried out such studies generally reported poor perception, suggesting a clear deficit in current CI sound processing systems. In this study, a convolutional neural network (CNN)-based NLS classification model is used as a framework to compare unprocessed and CI-simulated NLS classification and evaluate NLS perception targeted algorithms among CI listeners. Additionally, a NLS enhancement algorithm that focuses on improving identifiability and perception among CI listeners is proposed. The proposed NLS enhancement algorithm is evaluated based on identifiability performance using the CI-simulated NLS classification model. The proposed NLS classification framework was able to achieve near human-level performance with no significant effect of classification modality (model vs human subject) and achieved mean classification scores of 85.86% for NH (p = 0.3758) and 65.25% for CI (p = 0.1725). Among the four different feature-based methods of the proposed NLS enhancement algorithm, the "harmonicity"-based one achieved highest mean classification accuracy of 63.75%, when compared to baseline, and demonstrated significant improvement in performance (p = 0.0403). The resulting proposed comparative NLS classification framework contributes toward (i) advancement of NLS recognition studies, (ii) mitigation of CI user recruitment constraints and listener evaluation with NH listeners, (iii) development of a community shared testbed for comparative NLS studies, and (iv) advancement of NLS enhancement studies (identifiability and perceptual factors) among CI listeners.

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.

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.

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.

Environmental Sound Awareness in Experienced Cochlear Implant Users and Cochlear Implant Candidates

OBJECTIVE

To determine if postlingually deaf adult cochlear implant (CI) users have better environmental sound awareness (ESA) compared with adult patients eligible for CIs who have not yet undergone implantation.

STUDY DESIGN

Cross-sectional cohort study.

SETTING

Tertiary referral center.

PATIENTS

A group of 39 postlingually deaf adult patients who are experienced CI users (ECI), and a group of 20 postlingually deaf adult patients who are cochlear implant candidates (CIC) awaiting implantation.

INTERVENTION

Cochlear implantation.

MAIN OUTCOME MEASURE

Environmental sound awareness as measured by accuracy (percent correct) using the computerized, Familiar Environmental Sounds Test-Identification (FEST-I).

RESULTS

There was no significant difference between ESA in our sample of ECI users versus CIC patients. The ECI users scored an average FEST-I accuracy of 59.9% (SD 14.3). In comparison, the CICs had an average FEST-I accuracy of 54.7% (SD 26.4). This difference was not statistically significant.

CONCLUSIONS

Our findings suggest that, despite the commonly held notion that improved ESA may be a benefit of cochlear implantation, our sample of ECI users did not demonstrate superior performance compared with CICs.

A Mathematical Approach to Correlating Objective Spectro-Temporal Features of Non-linguistic Sounds With Their Subjective Perceptions in Humans

Non-linguistic sounds (NLSs) are a core feature of our everyday life and many evoke powerful cognitive and emotional outcomes. The subjective perception of NLSs by humans has occasionally been defined for single percepts, e.g., their pleasantness, whereas many NLSs evoke multiple perceptions. There has also been very limited attempt to determine if NLS perceptions are predicted from objective spectro-temporal features. We therefore examined three human perceptions well-established in previous NLS studies ("Complexity," "Pleasantness," and "Familiarity"), and the accuracy of identification, for a large NLS database and related these four measures to objective spectro-temporal NLS features, defined using rigorous mathematical descriptors including stimulus entropic and algorithmic complexity measures, peaks-related measures, fractal dimension estimates, and various spectral measures (mean spectral centroid, power in discrete frequency ranges, harmonicity, spectral flatness, and spectral structure). We mapped the perceptions to the spectro-temporal measures individually and in combinations, using complex multivariate analyses including principal component analyses and agglomerative hierarchical clustering.

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.

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.

Mandarin speech-in-noise and tone recognition using vocoder simulations of the temporal limits encoder for cochlear implants

Temporal envelope-based signal processing strategies are widely used in cochlear-implant (CI) systems. It is well recognized that the inability to convey temporal fine structure (TFS) in the stimuli limits CI users' performance, but it is still unclear how to effectively deliver the TFS. A strategy known as the temporal limits encoder (TLE), which employs an approach to derive the amplitude modulator to generate the stimuli coded in an interleaved-sampling strategy, has recently been proposed. The TLE modulator contains information related to the original temporal envelope and a slow-varying TFS from the band signal. In this paper, theoretical analyses are presented to demonstrate the superiority of TLE compared with two existing strategies, the clinically available continuous-interleaved-sampling (CIS) strategy and the experimental harmonic-single-sideband-encoder strategy. Perceptual experiments with vocoder simulations in normal-hearing listeners are conducted to compare the performance of TLE and CIS on two tasks (i.e., Mandarin speech reception in babble noise and tone recognition in quiet). The performance of the TLE modulator is mostly better than (for most tone-band vocoders) or comparable to (for noise-band vocoders) the CIS modulator on both tasks. This work implies that there is some potential for improving the representation of TFS with CIs by using a TLE strategy.

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.

Perception of everyday sounds: a developmental study of a free sorting task

OBJECTIVES

The analysis of categorization of everyday sounds is a crucial aspect of the perception of our surrounding world. However, it constitutes a poorly explored domain in developmental studies. The aim of our study was to understand the nature and the logic of the construction of auditory cognitive categories for natural sounds during development. We have developed an original approach based on a free sorting task (FST). Indeed, categorization is fundamental for structuring the world and cognitive skills related to, without having any need of the use of language. Our project explored the ability of children to structure their acoustic world, and to investigate how such structuration matures during normal development. We hypothesized that age affects the listening strategy and the category decision, as well as the number and the content of individual categories.

DESIGN

Eighty-two French children (6-9 years), 20 teenagers (12-13 years), and 24 young adults participated in the study. Perception and categorization of everyday sounds was assessed based on a FST composed of 18 different sounds belonging to three a priori categories: non-linguistic human vocalizations, environmental sounds, and musical instruments.

RESULTS

Children listened to the sounds more times than older participants, built significantly more classes than adults, and used a different strategy of classification. We can thus conclude that there is an age effect on how the participants accomplished the task. Analysis of the auditory categorization performed by 6-year-old children showed that this age constitutes a pivotal stage, in agreement with the progressive change from a non-logical reasoning based mainly on perceptive representations to the logical reasoning used by older children. In conclusion, our results suggest that the processing of auditory object categorization develops through different stages, while the intrinsic basis of the classification of sounds is already present in childhood.

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.

The influence of environmental sound training on the perception of spectrally degraded speech and environmental sounds

Perceptual training with spectrally degraded environmental sounds results in improved environmental sound identification, with benefits shown to extend to untrained speech perception as well. The present study extended those findings to examine longer-term training effects as well as effects of mere repeated exposure to sounds over time. Participants received two pretests (1 week apart) prior to a week-long environmental sound training regimen, which was followed by two posttest sessions, separated by another week without training. Spectrally degraded stimuli, processed with a four-channel vocoder, consisted of a 160-item environmental sound test, word and sentence tests, and a battery of basic auditory abilities and cognitive tests. Results indicated significant improvements in all speech and environmental sound scores between the initial pretest and the last posttest with performance increments following both exposure and training. For environmental sounds (the stimulus class that was trained), the magnitude of positive change that accompanied training was much greater than that due to exposure alone, with improvement for untrained sounds roughly comparable to the speech benefit from exposure. Additional tests of auditory and cognitive abilities showed that speech and environmental sound performance were differentially correlated with tests of spectral and temporal-fine-structure processing, whereas working memory and executive function were correlated with speech, but not environmental sound perception. These findings indicate generalizability of environmental sound training and provide a basis for implementing environmental sound training programs for cochlear implant (CI) patients.

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.