Music sound quality assessment in bimodal cochlear implant users – toward improved hearing aid fitting

The use of cochlear implants (CI) is the common treatment to counteract severe-profound hearing loss. CI often allow reasonable speech understanding but are generally limited in terms of spectro-temporal resolution. Many CI recipients use a hearing aid (HA) on the non-implanted ear (so called bimodal patients) that complements the electrical stimulation of the CI by providing acoustical fine structure information. Amongst others, this might be especially beneficial for music appraisal. However, it is not clear how the HA should be fitted in conjunction with the CI in order to provide the best sound quality. The purpose of this study was to vary different fitting parameters of the HA systematically and to determine the resulting music sound quality. To this end, a master hearing aid was used in order to have controlled access to the different parameters. Three different music excerpts (pop with and without vocals, classic) were presented to 13 bimodally fitted CI users and the sound quality was assessed using the “multiple-stimulus with hidden reference and anchor” (MUSHRA) test. Since the goal was to gain information on possible improvement of fitting, a complete retest was performed and individual reliability of the assessments was determined by the eGauge method. It could be shown that most of the listeners were able to provide reliable sound quality judgements. In terms of HA fitting it turned out that changing compression and varying low frequency gain had a significant effect compared to a standard prescriptive fitting based on DSL v5.0. However, especially the effect of changing low frequency gain depended on the music excerpts presented, since pop music with vocals revealed the largest effect. The study gives evidence that hearing aid fitting can be optimized relative to a standard prescriptive rule in order to improve music sound quality in bimodal CI users. Moreover, the method might be helpful in a clinical setting to determine the best fitting based on individual results. ### Competing Interest Statement The first author (KHAA) was financially supported by a research grant (IIR-1934) of Cochlear Ltd. The other authors declare no competing interests. The study was designed by the authors in collaboration with Cochlear Ltd. Data collection, analysis and the decision to publish were all solely accounted for by the authors. ### Clinical Trial DRKS00016778 ### Funding Statement This study was funded by Cochlear Ltd. (Reference IIR-1934) ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Institutional Review Board of the Medical Faculty of the University of Cologne (Reference 18-383). All subjects provided informed consent prior to participation. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the author