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Background and Purpose: The objective of several studies was to evaluate the improvement of hearing with cochlear implant (CI) and contralateral hearing aid (HA) in terms of speech understanding, listening comfort and sound quality. Features under investigation were a prescriptive fitting formula, accounting for the specific characteristics of bimodal listening, as well as ear-to-ear communication, allowing an exchange of microphone signals between two hearing instruments and with this the use of directional microphones as well as directivity steering. Methods: Directional microphones were tested in a variety of setups presenting different speech and noise signals from multiple loudspeakers. HA fittings were optimized by using the bimodal prescription. Speech understanding in noise, sound quality ratings and subjective preference were measured at 10 research sites in Belgium, Germany, the Netherlands and the USA. Results: Improvements in speech reception threshold (SRT) up to 5 dB were obtained in various noisy environments for a speaker at the front with directional microphones in comparison to the omni-directional setting. For a lateral speaker, improvements of around 2 dB and 4 dB were obtained with directivity steering features, respectively. CI users as well as professionals reported highly positive experience with the binaural technology. Conclusion: The binaural technology in CI systems led to improved speech understanding as well as a higher comfort for handling and hearing perception for the CI user. [ABSTRACT FROM AUTHOR]

Purpose of the study: Effective and efficient fitting methods for cochlear implant (CI) recipients with aidable contralateral acoustic hearing become more and more important in clinical practice. Recently, a dedicated bimodal fitting formula (APD Bimodal) has been introduced to improve bimodal benefit for patients and simplify the fitting process for audiologists. Materials and methods: Ten experienced adult bimodal CI recipients were fitted with the same hearing aid and participated in two acute appointments and a chronic trial between the visits. Speech understanding in noise and subjective preference were assessed in two conditions: prescriptive hearing aid fitting according to DSL v5 and APD Bimodal without any further fine-tuning. The Italian matrix test was administered with the international female fluctuating masking noise to assess speech understanding. Subjects indicated their preference for either formula in an A/B comparison task. The number and type of fine-tuning steps were analyzed to quantify the efficiency of the bimodal prescription in the fitting process. Results: Depending on audiogram and input level, DSL prescribes 5-10 dB more gain than APD Bimodal. While no significant and clinically relevant differences in speech understanding between DSL v5 and APD Bimodal were observed, the majority of subjects indicated a preference for the APD Bimodal, mainly because of a more comfortable loudness perception. However, there is trend that APDB provides better speech understanding at high noise levels, whereas DSL seems to perform better at low levels. Conclusion: The optimum gain for bimodal users with regards to speech perception seems to allow for variations of about 10 dB. This degree of freedom can be used to find the optimum trade-off between loudness comfort and audibility. A dedicated bimodal acoustic prescription was preferred by the majority of subjects due to more comfortable loudness than provided by DSL -- without degrading speech understanding in noise. [ABSTRACT FROM AUTHOR]

The benefits of combining a cochlear implant (CI) and a hearing aid (HA) in opposite ears on speech perception were examined in 15 adult unilateral CI recipients who regularly use a contralateral HA. A within-subjects design was carried out to assess speech intelligibility testing, listening effort ratings, and a sound quality questionnaire for the conditions CI alone, CIHA together, and HA alone when applicable. The primary outcome of bimodal benefit, defined as the difference between CIHA and CI, was statistically significant for speech intelligibility in quiet as well as for intelligibility in noise across tested spatial conditions. A reduction in effort on top of intelligibility at the highest tested signal-to-noise ratio was found. Moreover, the bimodal listening situation was rated to sound more voluminous, less tinny, and less unpleasant than CI alone. Listening effort and sound quality emerged as feasible and relevant measures to demonstrate bimodal benefit across a clinically representative range of bimodal users. These extended dimensions of speech perception can shed more light on the array of benefits provided by complementing a CI with a contralateral HA. [ABSTRACT FROM AUTHOR]

Objective: This study investigated a previously evaluated self-adjustment procedure with respect to its applicability for asymmetrical hearing loss (AHL). Self-adjusted settings were evaluated for speech recognition in noise and sound preference., Design: Participants were given the possibility to adjust the left and right hearing aid separately using a two-dimensional user interface. Two different adjustment sequences were tested. Realistic everyday sound scenes in a laboratory environment were presented. The difference between the ears regarding their speech recognition in noise was tested with two spatial conditions, unaided as well as with the prescriptive formula and the self-adjusted setting., Study Sample: Nineteen experienced hearing aid users (median age 76 years) with different degrees of AHL were invited to participate in this study., Results: Participants adjusted a higher gain slope across frequency in the worse ear than in the better one. The two adjustment sequences resulted in significantly different adjustment durations and gain settings. The difference between the ears regarding speech recognition in noise did not change with the self-adjustment. Overall, group-mean effect sizes were small compared to the parameter space., Conclusions: The adjustment procedure can be used also by hearing aid users with AHL to find a possibly preferred gain setting.

Background: Due to variation in electrode design, insertion depth and cochlear morphology, patients with a cochlear implant (CI) often have to adapt to a substantial mismatch between the characteristic response frequencies of cochlear neurons and the stimulus frequencies assigned to electrode contacts. We introduce an imaging-based fitting intervention, which aimed to reduce frequency-to-place mismatch by aligning frequency mapping with the tonotopic position of electrodes. Results were evaluated in a novel trial set-up where subjects crossed over between intervention and control using a daily within-patient randomized approach, immediately from the start of CI rehabilitation., Methods: Fourteen adult participants were included in this single-blinded, daily randomized clinical trial. Based on a fusion of pre-operative imaging and a post-operative cone beam CT scan (CBCT), mapping of electrical input was aligned to natural place-pitch arrangement in the individual cochlea. That is, adjustments to the CI's frequency allocation table were made so electrical stimulation of frequencies matched as closely as possible with corresponding acoustic locations in the cochlea. For a period of three months, starting at first fit, a scheme was implemented whereby the blinded subject crossed over between the experimental and standard fitting program using a daily randomized wearing schedule, and thus effectively acted as their own control. Speech outcomes (such as speech intelligibility in quiet and noise, sound quality and listening effort) were measured with both settings throughout the study period., Results: On a group level, standard fitting obtained subject preference and showed superior results in all outcome measures. In contrast, two out of fourteen subjects preferred the imaging-based fitting and correspondingly had better speech understanding with this setting compared to standard fitting., Conclusion: On average, cochlear implant fitting based on individual tonotopy did not elicit higher speech intelligibility but variability in individual results strengthen the potential for individualized frequency fitting. The novel trial design proved to be a suitable method for evaluation of experimental interventions in a prospective trial setup with cochlear implants., Competing Interests: The work of LL, JD, and ED in this investigator-initiated study was financially supported by a research grant from Advanced Bionics Inc. The study was designed in cooperation between MUMC and Advanced Bionics. Data collection, analysis, and the decision to publish were all solely accounted for by MUMC. The work presented in this manuscript is the intellectual property of MUMC. JC is employed at Advanced Bionics. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Lambriks, van Hoof, Debruyne, Janssen, Chalupper, van der Heijden, Hof, Hellingman, Devocht and George.)

Purpose: Speech understanding in noise and horizontal sound localization is poor in most cochlear implant (CI) users with a hearing aid (bimodal stimulation). This study investigated the effect of static and less-extreme adaptive frequency compression in hearing aids on spatial hearing. By means of frequency compression, we aimed to restore high-frequency audibility, and thus improve sound localization and spatial speech recognition., Method: Sound-detection thresholds, sound localization, and spatial speech recognition were measured in eight bimodal CI users, with and without frequency compression. We tested two compression algorithms: a static algorithm, which compressed frequencies beyond the compression knee point (160 or 480 Hz), and an adaptive algorithm, which aimed to compress only consonants leaving vowels unaffected (adaptive knee-point frequencies from 736 to 2946 Hz)., Results: Compression yielded a strong audibility benefit (high-frequency thresholds improved by 40 and 24 dB for static and adaptive compression, respectively), no meaningful improvement in localization performance (errors remained > 30 deg), and spatial speech recognition across all participants. Localization biases without compression (toward the hearing-aid and implant side for low- and high-frequency sounds, respectively) disappeared or reversed with compression. The audibility benefits provided to each bimodal user partially explained any individual improvements in localization performance; shifts in bias; and, for six out of eight participants, benefits in spatial speech recognition., Conclusions: We speculate that limiting factors such as a persistent hearing asymmetry and mismatch in spectral overlap prevent compression in bimodal users from improving sound localization. Therefore, the benefit in spatial release from masking by compression is likely due to a shift of attention to the ear with the better signal-to-noise ratio facilitated by compression, rather than an improved spatial selectivity. Supplemental Material https://doi.org/10.23641/asha.16869485.

Objective: The subjective experiences were assessed of cochlear implant (CI) users either wearing or not wearing a hearing aid (HA) at the contralateral ear., Design: Unilateral CI-recipients were asked to fill out a set of daily-life questionnaires on bimodal HA use, hearing disability, hearing handicap and general quality of life., Study Sample: Twenty-six CI-recipients who regularly use a contralateral HA (bimodal group) and twenty-two CI-recipients who do not use a HA in the contralateral ear (unilateral group)., Results: Comparisons between both groups (bimodal versus unilateral) showed no difference in self-rated disability, hearing handicap or general quality of life. However within the group of bimodal listeners, participants did report a benefit of bimodal hearing ability in various daily life listening situations., Conclusions: Bimodal benefit in daily life can consistently be experienced and reported within the group of bimodal users., Competing Interests: A research grant from Advanced Bionics Inc. to MUMC+ financially supported the work of the first author (E.D.) in this investigator-initiated study. The second author (M.J.) reviewed the manuscript and provided statistical support, made possible by a grant from the Dutch Heinsius-Houbolt Foundation. The third author (J.C.) had a role in designing the study. He holds a scientific post in the Advanced Bionics European Research Center. For the remaining authors no conflicts were declared. The study was designed in cooperation between MUMC+ and Advanced Bionics. Data collection, analysis and the decision to publish were all solely accounted for by MUMC+. The work presented in this manuscript is the intellectual property of MUMC+.

The population of unilateral cochlear implant (CI) users with aidable residual hearing in the contralateral ear is continuously growing. Aiding the contralateral ear with a hearing aid has been shown to provide substantial benefit regarding speech intelligibility in quiet and in noise, sound quality, localization ability and listening effort. In this study, a dedicated hearing aid with the accompanying fitting prescription, tailored to the needs of bimodal listeners was evaluated in nine bimodal CI users. Speech intelligibility scores in noise revealed on-par performance of the dedicated bimodal fitting compared to the clinical standard prescription. 78% of the bimodal CI users preferred the dedicated bimodal fitting over the clinical standard. The minimal subject-specific finetuning effort required during the dedicated bimodal fitting process emphasizes the clinical efficiency., Competing Interests: Conflict of interest: Josef Chalupper declares grants from Advanced Bionics. The other authors did not receive any grants from Advanced Bionics.

Objectives: This study aimed to improve access to high-frequency interaural level differences (ILD), by applying extreme frequency compression (FC) in the hearing aid (HA) of 13 bimodal listeners, using a cochlear implant (CI) and conventional HA in opposite ears., Design: An experimental signal-adaptive frequency-lowering algorithm was tested, compressing frequencies above 160 Hz into the individual audible range of residual hearing, but only for consonants (adaptive FC), thus protecting vowel formants, with the aim to preserve speech perception. In a cross-over design with at least 5 weeks of acclimatization between sessions, bimodal performance with and without adaptive FC was compared for horizontal sound localization, speech understanding in quiet and in noise, and vowel, consonant and voice-pitch perception., Results: On average, adaptive FC did not significantly affect any of the test results. Yet, two subjects who were fitted with a relatively weak frequency compression ratio, showed improved horizontal sound localization. After the study, four subjects preferred adaptive FC, four preferred standard frequency mapping, and four had no preference. Noteworthy, the subjects preferring adaptive FC were those with best performance on all tasks, both with and without adaptive FC., Conclusion: On a group level, extreme adaptive FC did not change sound localization and speech understanding in bimodal listeners. Possible reasons are too strong compression ratios, insufficient residual hearing or that the adaptive switching, although preserving vowel perception, may have been ineffective to produce consistent ILD cues. Individual results suggested that two subjects were able to integrate the frequency-compressed HA input with that of the CI, and benefitted from enhanced binaural cues for horizontal sound localization.

The benefits of combining a cochlear implant (CI) and a hearing aid (HA) in opposite ears on speech perception were examined in 15 adult unilateral CI recipients who regularly use a contralateral HA. A within-subjects design was carried out to assess speech intelligibility testing, listening effort ratings, and a sound quality questionnaire for the conditions CI alone, CIHA together, and HA alone when applicable. The primary outcome of bimodal benefit, defined as the difference between CIHA and CI, was statistically significant for speech intelligibility in quiet as well as for intelligibility in noise across tested spatial conditions. A reduction in effort on top of intelligibility at the highest tested signal-to-noise ratio was found. Moreover, the bimodal listening situation was rated to sound more voluminous, less tinny, and less unpleasant than CI alone. Listening effort and sound quality emerged as feasible and relevant measures to demonstrate bimodal benefit across a clinically representative range of bimodal users. These extended dimensions of speech perception can shed more light on the array of benefits provided by complementing a CI with a contralateral HA.

Objective: To evaluate monaural beamforming in bimodally aided cochlear implant (CI) users., Design: The study enrolled twelve adult bimodal listeners with at least six months of CI-experience and using a contralateral hearing aid (HA) most of the daytime. Participants were uniformly fitted with the same CI speech processor and HA, giving access to an identical monaural beamformer in both ears. A within-subject repeated measures design evaluated three directional configurations [omnidirectional, asymmetric directivity (in CI alone) and symmetric directivity (in both CI and HA)] in two noise types [stationary and fluctuating]. Bimodal speech reception thresholds (SRT) as well as listening effort ratings were assessed in a diffuse noise field., Results: Symmetric monaural beamforming provided a significant SRT improvement of 2.6 dB SNR, compared to 1.6 dB SNR for asymmetric monaural beamforming. Directional benefits were similarly observed in stationary and fluctuating noise. Directivity did not contribute to less listening effort in addition to improvement in speech intelligibility. Bimodal performance was about 7 dB SNR worse in fluctuating than in stationary noise., Conclusions: Monaural beamforming provided substantial benefit for speech intelligibility in noise for bimodal listeners. The greatest benefit occurred when monaural beamforming was activated symmetrically in both CI and HA. Monaural beamforming does not bridge the gap between bimodal and normal hearing performance, especially in fluctuating noise. Results advocate further bimodal co-operation., Trial Registration: This trial was registered in www.trialregister.nl under number NTR4901.

Conclusion In users of a cochlear implant (CI) and a hearing aid (HA) in contralateral ears, frequency-dependent loudness balancing between devices did, on average, not lead to improved speech understanding as compared to broadband balancing. However, nine out of 15 bimodal subjects showed significantly better speech understanding with either one of the fittings. Objectives Sub-optimal fittings and mismatches in loudness are possible explanations for the large individual differences seen in listeners using bimodal stimulation. Methods HA gain was adjusted for soft and loud input sounds in three frequency bands (0-548, 548-1000, and >1000 Hz) to match loudness with the CI. This procedure was compared to a simple broadband balancing procedure that reflected current clinical practice. In a three-visit cross-over design with 4 weeks between sessions, speech understanding was tested in quiet and in noise and questionnaires were administered to assess benefit in real world. Results Both procedures resulted in comparable HA gains. For speech in noise, a marginal bimodal benefit of 0.3 ± 4 dB was found, with large differences between subjects and spatial configurations. Speech understanding in quiet and in noise did not differ between the two loudness balancing procedures.

Interaural differences in sound arrival time (ITD) and in level (ILD) enable us to localize sounds in the horizontal plane, and can support source segregation and speech understanding in noisy environments. It is uncertain whether these cues are also available to hearing-impaired listeners who are bimodally fitted, i.e. with a cochlear implant (CI) and a contralateral hearing aid (HA). Here, we assessed sound localization behavior of fourteen bimodal listeners, all using the same Phonak HA and an Advanced Bionics CI processor, matched with respect to loudness growth. We aimed to determine the availability and contribution of binaural (ILDs, temporal fine structure and envelope ITDs) and monaural (loudness, spectral) cues to horizontal sound localization in bimodal listeners, by systematically varying the frequency band, level and envelope of the stimuli. The sound bandwidth had a strong effect on the localization bias of bimodal listeners, although localization performance was typically poor for all conditions. Responses could be systematically changed by adjusting the frequency range of the stimulus, or by simply switching the HA and CI on and off. Localization responses were largely biased to one side, typically the CI side for broadband and high-pass filtered sounds, and occasionally to the HA side for low-pass filtered sounds. HA-aided thresholds better than 45 dB HL in the frequency range of the stimulus appeared to be a prerequisite, but not a guarantee, for the ability to indicate sound source direction. We argue that bimodal sound localization is likely based on ILD cues, even at frequencies below 1500 Hz for which the natural ILDs are small. These cues are typically perturbed in bimodal listeners, leading to a biased localization percept of sounds. The high accuracy of some listeners could result from a combination of sufficient spectral overlap and loudness balance in bimodal hearing., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Objectives: The purpose of this study was to improve bimodal benefit in listeners using a cochlear implant (CI) and a hearing aid (HA) in contralateral ears, by matching the time constants and the number of compression channels of the automatic gain control (AGC) of the HA to the CI. Equivalent AGC was hypothesized to support a balanced loudness for dynamically changing signals like speech and improve bimodal benefit for speech understanding in quiet and with noise presented from the side(s) at 90 degree., Design: Fifteen subjects participated in the study, all using the same Advanced Bionics Harmony CI processor and HA (Phonak Naida S IX UP). In a 3-visit crossover design with 4 weeks between sessions, performance was measured using a HA with a standard AGC (syllabic multichannel compression with 1 ms attack time and 50 ms release time) or an AGC that was adjusted to match that of the CI processor (dual AGC broadband compression, 3 and 240 msec attack time, 80 and 1500 msec release time). In all devices, the AGC was activated above the threshold of 63 dB SPL. The authors balanced loudness across the devices for soft and loud input sounds in 3 frequency bands (0 to 548, 548 to 1000, and >1000 Hz). Speech understanding was tested in free field in quiet and in noise for three spatial speaker configurations, with target speech always presented from the front. Single-talker noise was either presented from the CI side or the HA side, or uncorrelated stationary speech-weighted noise or single-talker noise was presented from both sides. Questionnaires were administered to assess differences in perception between the two bimodal fittings., Results: Significant bimodal benefit over the CI alone was only found for the AGC-matched HA for the speech tests with single-talker noise. Compared with the standard HA, matched AGC characteristics significantly improved speech understanding in single-talker noise by 1.9 dB when noise was presented from the HA side. AGC matching increased bimodal benefit insignificantly by 0.6 dB when noise was presented from the CI implanted side, or by 0.8 (single-talker noise) and 1.1 dB (stationary noise) in the more complex configurations with two simultaneous maskers from both sides. In questionnaires, subjects rated the AGC-matched HA higher than the standard HA for understanding of one person in quiet and in noise, and for the quality of sounds. Listening to a slightly raised voice, subjects indicated increased listening comfort with matched AGCs. At the end of the study, 9 of 15 subjects preferred to take home the AGC-matched HA, 1 preferred the standard HA and 5 subjects had no preference., Conclusion: For bimodal listening, the AGC-matched HA outperformed the standard HA in speech understanding in noise tasks using a single competing talker and it was favored in questionnaires and in a subjective preference test. When noise was presented from the HA side, AGC matching resulted in a 1.9 dB SNR additional benefit, even though the HA was at the least favorable SNR side in this speaker configuration. Our results possibly suggest better binaural processing for matched AGCs.