Investigations on sound quality optimisation in bimodal Cochlear Implant fitting

In many cases, cochlear implants enable a significant improvement in speech recognition. However, sound quality is fundamentally restricted due to limited spectro-temporal cues. A conventional hearing aid is often used on the contralateral side, which opens up potential for improving sound quality through the additional transmission of acoustic features. In this context, two experiments aimed to systematically optimise the hearing aid fitting in the low-frequency range. The fitting based on the DSL v5.0 rule (Scolie et al., 2005) was always used as a reference. In the first experiment, a Master Hearing Aid (Grimm et al., 2006) was applied to simulate the hearing aid on the non-implanted side. This allowed all changes to the fitting to be carried out under controlled conditions. Building on this, real hearing aids were used in the second experiment to verify the results under conditions closer to everyday life. Various pieces of music were presented and the subjective perception of sound was recorded using different psychoacoustic methods (Abdellatif et al., 2022). Based on both experiments, it is shown that an increase in low-frequency gain relative to that proposed via DSL can lead to an improvement in sound quality 1 2 3.