Perception of second-formant transitions by hearing-impaired persons

Just-noticeable difference in starting frequency of the F2 transition was measured in four moderately hearing-impaired and four normal-hearing adults at a stimulus presentation level of 85 dB SPL. Just-noticeable difference was established for two stimulus configurations (F2 in isolation and F1 + F2) at two F2 starting frequency locations of the standard stimulus (1100 Hz and the subject's /ba/-/da/ phoneme boundary). There were no significant differences in discrimination performance across the four stimulus conditions within either subject group; the F1 upward spread of masking effect described by previous investigators was not demonstrated by the averaged group data from this study. The high variability in performance among hearing-impaired subjects implies that: (1) subjects with similar audiometric configurations do not necessarily perform similarly on auditory tasks involving synthetic speech stimuli; and (2) discriminability of changes in F2 may not be an appropriate index of upward spread of masking by F1 of F2.