In general, the FSP strategy and the 2 settings of the FS4 strategy provided similar levels in the perception of prosody and timbre cues, as well as in the identification of instruments.
Advances in speech coding strategies and electrode array designs for cochlear implants (CIs) predominantly aim at improving speech perception. Current efforts are also directed at transmitting appropriate cues of the fundamental frequency (F0) to the auditory nerve with respect to speech quality, prosody, and music perception. The aim of this study was to examine the effects of various electrode configurations and coding strategies on speech intonation identification, speaker gender identification, and music quality rating. In six MED-EL CI users electrodes were selectively deactivated in order to simulate different insertion depths and inter-electrode distances when using the high definition continuous interleaved sampling (HDCIS) and fine structure processing (FSP) speech coding strategies. Identification of intonation and speaker gender was determined and music quality rating was assessed. For intonation identification HDCIS was robust against the different electrode configurations, whereas fine structure processing showed significantly worse results when a short electrode depth was simulated. In contrast, speaker gender recognition was not affected by electrode configuration or speech coding strategy. Music quality rating was sensitive to electrode configuration. In conclusion, the three experiments revealed different outcomes, even though they all addressed the reception of F0 cues. Rapid changes in F0, as seen with intonation, were the most sensitive to electrode configurations and coding strategies. In contrast, electrode configurations and coding strategies did not show large effects when F0 information was available over a longer time period, as seen with speaker gender. Music quality relies on additional spectral cues other than F0, and was poorest when a shallow insertion was simulated.
Purpose
This study aims to investigate the effect of upgrading from the fine structure processing (FSP) coding strategy to the novel fine structure strategy “FS4” in adults in adults with cochlear implants manufactured by MED-EL GmbH (Innsbruck, Austria).
Method
A crossover, double-blinded study was conducted for 12 weeks. Twelve adult participants were randomly assigned to two groups. During the first 6-week test interval, one group continued to use their everyday FSP strategy, whereas the other group was upgraded to the FS4 strategy. In the second 6-week interval, the two groups switched coding strategies. Speech perception was measured at the end of each test interval with the Oldenburg Sentence Test and the Göttingen Sentence Test. Participants completed the Speech, Spatial and Qualities of Hearing Scale at the end of each test interval and a simple preference test at the end of the study.
Results
There was no significant difference in speech perception test results obtained with the Oldenburg Sentence Test and the Göttingen Sentence Test, neither in quiet nor in noise. Participants' Speech, Spatial and Qualities of Hearing Scale self-evaluation and preference test results showed that the two coding strategies had similar effects on their hearing perception. No clear preference for either of the strategies was found.
Conclusions
Speech perception test results and the participants' level of satisfaction were similar for the two FS coding strategies. Despite differences in the presentation of temporal fine structure between FSP and FS4, a clear benefit of the newer FS4 strategy could not be shown.
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