Effects of Interaural Timing Delays on Speech Perception in Noise in Bilateral Cochlear Implant Users

Precise interaural timing and level cues are critical for spatial hearing and speech understanding in noise. Bilateral cochlear implant (CI) users provide a controlled model to investigate how artificially introduced interaural timing disparities affect binaural hearing. This study investigates whether introducing a unilateral time delay in CI stimulation affects speech perception in noise and spatial release from masking (SRM).

Eleven bilateral CI users were tested using the German Oldenburger sentence test (OLSA) under three spatial noise conditions (S0N0, S0N+90, S0N-90), with and without a 10 ms delay introduced to the right CI processor. Speech reception thresholds (SRTs) and SRM were analyzed using repeated-measures ANOVA.

No significant differences in SRT or SRM were found between the delay and non-delay conditions across all spatial configurations. A consistent right-ear advantage was observed, but the induced interaural delay did not significantly impair speech-in-noise performance.

A unilateral 10 ms delay in CI stimulation does not significantly affect speech perception or SRM in bilateral CI users. These findings indicate that a unilateral 10 ms interaural delay does not measurably affect speech perception or spatial release from masking in bilateral CI users. This observation is consistent with previous reports suggesting limited functional use of fine-grained interaural timing cues during speech-in-noise processing, although the present study cannot draw conclusions about smaller interaural delays.