Bimodal Benefit for Music Perception: Effect of Acoustic Bandwidth

Purpose The challenges associated with cochlear implant (CI)–mediated listening are well documented; however, they can be mitigated through the provision of aided acoustic hearing in the contralateral ear—a configuration termed bimodal hearing . This study extends previous literature to examine the effect of acoustic bandwidth in the non-CI ear for music perception. The primary aim was to determine the minimum and optimum acoustic bandwidth necessary to obtain bimodal benefit for music perception and speech perception. Method Participants included 12 adult bimodal listeners and 12 adult control listeners with normal hearing. Music perception was assessed via measures of timbre perception and subjective sound quality of real-world music samples. Speech perception was assessed via monosyllabic word recognition in quiet. Acoustic stimuli were presented to the non-CI ear in the following filter conditions: < 125, < 250, < 500, and < 750 Hz, and wideband (full bandwidth). Results Generally, performance for all stimuli improved with increasing acoustic bandwidth; however, the bandwidth that is both minimally and optimally beneficial may be dependent upon stimulus type. On average, music sound quality required wideband amplification, whereas speech recognition with a male talker in quiet required a narrower acoustic bandwidth (< 250 Hz) for significant benefit. Still, average speech recognition performance continued to improve with increasing bandwidth. Conclusion Further research is warranted to examine optimal acoustic bandwidth for additional stimulus types; however, these findings indicate that wideband amplification is most appropriate for speech and music perception in individuals with bimodal hearing.

Efficacy of Auditory Verbal Therapy on Listening and Linguistic Skills of a Child with Bimodal Hearing

Introduction This study aimed to document the effect of Auditory Verbal Therapy (AVT) with proper assessment and management in early intervention of a child with bimodal hearing. Bimodal Hearing is the use of a cochlear implant in one ear and a hearing aid in the opposite ear. Auditory Verbal Therapy is a highly specialist early intervention programme which equips parents with the skills to maximise their deaf child’s speech and language development. Case Report A male child aged 5 years 1 month had bilateral severe to profound hearing loss and speech-language problem. He was using cochlear implant in the right ear and BTE hearing aid in left ear (Bimodal hearing). Speech and language assessment revealed delayed semantic, syntax and pragmatic skills. Assessment of language development test showed poor receptive and expressive language score. The functional auditory performance indicator score indicated poor auditory function. Auditory verbal therapy hierarchy plan was used for treatment. Post 15 sessions after applying AVT the child’s listening and linguistic skills showed a great improvement. Discussion The scales used to measure the efficacy of AVT are found to be useful for the assessment and goal setting for intervention. Thus, appropriate quantification of various aspects of communication skills may describe its potential impact in this case under ADIP scheme.

A Literature Review of Bimodal Fitting

Although there are quite a few bimodal cochlear implant users, bimodal fitting guidelines were not fully developed. Bimodal fitting optimization is one of the factors that contribute to successful bimodal outcomes. The purpose of this study is to investigate recent literatures related to bimodal fitting to establish evidence based bimodal fitting guidelines. Three databases including Google Scholar, PubMed publisher, and PLOS One were searched to review bimodal fitting literatures. A total of 599,604 articles were identified by using ten bimodal relevant keywords at the initial stage. Then, we included 192 articles with abstract review, inclusion and exclusion criteria and removals of duplicates. Lastly, two authors reviewed full texts and identified a total of 19 bimodal fitting articles. Results were categorized into type of bimodal intervention, procedures, and outcomes. Bimodal fitting procedures, test materials, and questionnaires were also summarized. A total of 18 articles consist of bimodal hearing aid fitting covering hearing aid fitting formula, gain adjustment, loudness balance, frequency band, frequency lowering technology, and overall bimodal fitting guidelines. Only one article includes bimodal cochlear implant fitting with low frequency band adjustment. Several factors including real-ear measurement, loudness balance test, frequency band selection considering cochlear dead region, and subjective questionnaires are considered to optimize bimodal hearing aid fitting. Bimodal fitting guidelines considering several relevant factors will optimize bimodal fitting and improve bimodal benefits.

The Temporal Fine Structure of Background Noise Determines the Benefit of Bimodal Hearing for Recognizing Speech

Cochlear implant (CI) users have more difficulty understanding speech in temporally modulated noise than in steady-state (SS) noise. This is thought to be caused by the limited low-frequency information that CIs provide, as well as by the envelope coding in CIs that discards the temporal fine structure (TFS). Contralateral amplification with a hearing aid, referred to as bimodal hearing, can potentially provide CI users with TFS cues to complement the envelope cues provided by the CI signal. In this study, we investigated whether the use of a CI alone provides access to only envelope cues and whether acoustic amplification can provide additional access to TFS cues. To this end, we evaluated speech recognition in bimodal listeners, using SS noise and two amplitude-modulated noise types, namely babble noise and amplitude-modulated steady-state (AMSS) noise. We hypothesized that speech recognition in noise depends on the envelope of the noise, but not on its TFS when listening with a CI. Secondly, we hypothesized that the amount of benefit gained by the addition of a contralateral hearing aid depends on both the envelope and TFS of the noise. The two amplitude-modulated noise types decreased speech recognition more effectively than SS noise. Against expectations, however, we found that babble noise decreased speech recognition more effectively than AMSS noise in the CI-only condition. Therefore, we rejected our hypothesis that TFS is not available to CI users. In line with expectations, we found that the bimodal benefit was highest in babble noise. However, there was no significant difference between the bimodal benefit obtained in SS and AMSS noise. Our results suggest that a CI alone can provide TFS cues and that bimodal benefits in noise depend on TFS, but not on the envelope of the noise.

Comparison of Speech Perception Abilities of Children using Bimodal Hearing with Children using Cochlear Implant Alone

Introduction There are very few studies comparing speech perception abilities of children using bimodal hearing over monaural cochlear implant and factors related to benefit of bimodal hearing. The aim of this study is to compare speech perception abilities of children using bimodal fitting versus children using cochlear implant alone and explore factors related to benefit of bimodal hearing. Materials and Methods In the present study, 20 cochlear implantees with the hearing age range of 3 to 8 years were included. Speech perception performance was assessed by means of Parent’s Evaluation of Aural/Oral Performance of Children scale and early speech perception (ESP) test: Pattern Perception Words, Monosyllabic Words, Bisyllabic, and Trisyllabic Words Identification test. ESP test was carried out in two conditions cochlear implant with hearing aid in opposite ear (CIHA), bimodal, and cochlear implant (CI) alone. Aided audiometry was also carried out in above mentioned two conditions. Results and Discussion On aided audiometry test, aided thresholds were improved by 5 to 6 dB in CIHA condition as compared to CI alone condition in 14 out of 20 children. Whereas on speech perception test, there was a significant improvement of 15 to 20% on domains of ESP test in these children. Factors such as implant age, chronological age, and number of hours of hearing aid usage were not significantly associated with benefit. Nevertheless aided threshold at 4,000 Hz was found to be significantly associated with bimodal benefit. Conclusion Bimodal hearing is beneficial in most of the children than monaural hearing through cochlear implant.