Microphone directionality improves speech perception in Mandarin-speaking cochlear implant users

Abstract

Speech understanding in noise remains challenging for cochlear implant (CI) users. To address this, microphone directionality has been integrated into speech processors to improve the signal-to-noise ratio. Despite demonstrated benefits for users of non-tonal language, studies investigating its efficacy for users of tonal languages are limited. In this study, we evaluated the benefit of microphone directionality in 24 Mandarin-speaking adult CI users with uni- or bilateral post-lingual deafness (≥ 6 months of experience) using the Mandarin Speech Test Materials in quiet and noise. Speech and noise were presented simultaneously (S0N180). Results of the MSTM are presented as speech recognition score (SRS) as percentage correct. Performance with an omnidirectional speech processor (OPUS 2) was compared to one (SONNET) with three directional modes (omni, natural, adaptive). A visual analogue scale (VAS) questionnaire was used to assess preferences for each speech processor setting. Directional modes significantly improved speech perception in noise: SONNET/natural outperformed both OPUS 2 by 10.4% (95% CI: 3.4% to 17.5%; p = 0.006) and SONNET/omni by 12.4% (95% CI: 6.0% to 18.7%; p = 0.001), while SONNET/adaptive outperformed both OPUS 2 (by 13.6%; 95% CI: 7.9% to 19.3%; p < 0.001) and SONNET/omni (by 15.6%; 95% CI: 8.4% to 22.7%; p < 0.001). The difference between SONNET/adaptive and SONNET/natural was 3.17% points (95% CI: -2.2% to 8.5%; p  = 0.231). No significant difference was observed in quiet. 63% of participants favored SONNET/adaptive in noise. Under the S0N180 conditions tested, directional microphone settings were associated with better speech perception in noise than omnidirectional settings in Mandarin-speaking CI users, whereas no statistically significant difference was observed between the SONNET/adaptive and SONNET/natural settings. Upgrading from an omnidirectional speech processor to one equipped with directional technology may provide substantial and clinically meaningful benefit.