Speech and melody recognition in binaurally combined acoustic and electric hearing

TLDR

Speech recognition in noise and music perception is especially challenging for current cochlear implant users. The study investigates whether residual low‑frequency acoustic hearing combined with electric hearing improves performance over either mode alone in cochlear implant users. The authors evaluated speech recognition in noise and melody recognition in music by measuring performance with acoustic, electric, and combined hearing in five cochlear implant users. Residual low‑frequency acoustic hearing alone did not aid speech recognition in noise but markedly improved performance when combined with electric hearing, whereas it alone yielded better melody recognition than electric hearing, highlighting the need to encode fine‑structure cues in cochlear implants.

Abstract

Speech recognition in noise and music perception is especially challenging for current cochlear implant users. The present study utilizes the residual acoustic hearing in the nonimplanted ear in five cochlear implant users to elucidate the role of temporal fine structure at low frequencies in auditory perception and to test the hypothesis that combined acoustic and electric hearing produces better performance than either mode alone. The first experiment measured speech recognition in the presence of competing noise. It was found that, although the residual low-frequency (<1000 Hz) acoustic hearing produced essentially no recognition for speech recognition in noise, it significantly enhanced performance when combined with the electric hearing. The second experiment measured melody recognition in the same group of subjects and found that, contrary to the speech recognition result, the low-frequency acoustic hearing produced significantly better performance than the electric hearing. It is hypothesized that listeners with combined acoustic and electric hearing might use the correlation between the salient pitch in low-frequency acoustic hearing and the weak pitch in the envelope to enhance segregation between signal and noise. The present study suggests the importance and urgency of accurately encoding the fine-structure cue in cochlear implants.