FO processing and the separation of competing speech signals by listeners with normal hearing and with hearing loss.

Normal-hearing and hearing-impaired listeners were tested to determine F0 difference limens for synthetic tokens of 5 steady-state vowels. The same stimuli were then used in a concurrent-vowel labeling task with the F0 difference between concurrent vowels ranging between 0 and 4 semitones. Finally, speech recognition was tested for synthetic sentences in the presence of a competing synthetic voice with the same, a higher, or a lower F0. Normal-hearing listeners and hearing-impaired listeners with small F0-discrimination (deltaF0) thresholds showed improvements in vowel labeling when there were differences in F0 between vowels on the concurrent-vowel task. Impaired listeners with high deltaF0 thresholds did not benefit from F0 differences between vowels. At the group level, normal-hearing listeners benefited more than hearing-impaired listeners from F0 differences between competing signals on both the concurrent-vowel and sentence tasks. However, for individual listeners, deltaF0 thresholds and improvements in concurrent-vowel labeling based on F0 differences were only weakly associated with F0-based improvements in performance on the sentence task. For both the concurrent-vowel and sentence tasks, there was evidence that the ability to benefit from F0 differences between competing signals decreases with age.