Introduction

A cochlear implant (CI) restores bilateral hearing in listeners with either contralateral normal hearing (single sided deafness, SSD) or hearing impairment (bimodal, BIM) using a hearing aid (HA). This study investigated if patients of both groups with comparable binaural monosyllabic word recognition show differences for speech in noise or in speech.

Methods

Speech recognition thresholds (SRT) of 10 BIM and 9 SSD listeners were measured using the Oldenburg sentence test (OLSA). All participants had a monosyllabic word scoring in quiet ≥ 60% with the CI. Sentences of a male talker were presented against a) speech-shaped noise (SSN), b) a female talker, and c) a diffuse cafeteria noise. Speech was always presented from the front (S₀). The interferers a) and b) were either presented from the front (N₀), the CI side (N_CI), or the contralateral side (N_NH or N_HA).

Results

SSD subjects show SRTs between ‑18.7 and +5.3 dB for the symmetric conditions (S₀N₀, S₀N_Cafe), including significant differences between all interferer types. For the front/side conditions, the largest spatial release from masking (SRM) of 3.8 dB (median) was observed for SSN at S₀N_CI. BIM subjects show SRTs in the range of ‑9.9 to +6.6 dB for the symmetric conditions. In contrast to the SSD group, no significant difference between the female interferer and the SSN condition was observed. The largest masking release of 5.3 dB (median) was found for SSN at S₀N_HA.

Conclusions

SRTs of SSD and BIM subjects strongly depend on the interferer condition. The groups show comparable spatial masking release effects. Monosyllabic word recognition in quiet is a bad guess for binaural performance.

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