Cochlear implants (CIs) provide precise timing information that listeners rely on to understand speech. Some speech sounds are only differentiated by small differences in the timing of acoustic features. Previous studies have shown differences in the ability to perceive these timing cues depending on whether the speech sound was heard in a single word or embedded in a sentence. One explanation for the perceptual differences is forward masking. In forward masking, energy from a preceding non-overlapping sound masks perception of a following sound. This effect dissipates quickly; it disappears approximately 100 ms after the offset of the preceding speech. Therefore, this study tested perception of timing cues in listeners with CIs in words separated from preceding speech by 0, 25, 50, 75, and 100 ms. Differences in perception were observed such that the largest effects were seen at the shortest separation intervals. This pattern was only observed for speech sounds that immediately followed the preceding sound; in other words, at the beginning of the following word. The results of this study indicate that forward masking is a likely mechanism to explain the results of previous studies and could contribute to some of the difficulties that listeners with CIs experience when attempting to understand speech.

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