A New Fine Structure Speech Coding Strategy

Abstract

One of the most commonly used speech coding strategies for cochlear implants is continuous interleaved sampling (CIS), which codes the envelope information of an acoustic signal. Based on this strategy, MED-EL has recently developed the new fine structure processing (FSP) speech coding strategy, which also transmits subtle pitch and temporal cues. The aim of this study was to investigate the number of active channels necessary for good speech perception with FSP and whether there is an advantage for FSP compared with CIS at a reduced number of channels. Ten postlingually deafened patients using MED-EL Pulsar cochlear implants participated in this study. Patients were tested with all 12, 8, 5, 3, and 2 channels with CIS and FSP strategy, resulting in a total of 10 conditions. Performance was tested with numbers, monosyllables, and sentence tests. Our results showed an improvement in speech perception, with up to 5 channels for numbers and for monosyllables and sentence tests. Statistically significant increases in performance were noted from 3 to 8 channels for numbers, from 3 to 5 channels for monosyllables, and from 5 to 8 channels for sentence tests. No statistical significance was observed whether FSP or CIS was used. Based on these findings, the number of channels necessary for speech perception with FSP is similar to published results using CIS. There seems to be no advantage for FSP compared with CIS in the conditions of the present experiment.