The effects of speech-frequency masking on selected vocal characteristics of stutterers and nonstutterers
Gilmore, Keely Jade
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This study investigated the effects of speech- frequency masking on the vocal characteristics of a group of stutterers and nonstutterers. The six parameters selected for use in this study were disfluency, overall duration or rate, vowel duration, duration of vocal continuity, vocal continuity and intensity. Ten stutterers and ten nonstutterers served as subjects for this investigation. Each subject was tape recorded while reading a 232 word passage. The passage was read four times with intervals of four to ten days between readings. The first and third tapings were made with the subject not utilizing a masking device, while the second and fourth recordings were made using the device. Under conditions of masking both groups decreased their frequency of disfluency, with the group of stutterers demonstrating a significantly greater decrease overall. As a group stutterers decreased their vocal intensity, while nonstutterers increased their vocal intensity. With respect to rate, nonstutterers decreased their rate while stutterers increased their rate. Vowel duration tended to increase for both groups. It was noted that nonstutterers exhibited shorter overall vowel durations as compared to stutterers. Duration of vocal continuity between words was found to increase for both groups, with nonstutterers demonstrating this to a greater extent than stutterers. Under masking, vocal continuity was similar for both groups. To assess the effects of severity of stuttering on the parameters mentioned previously, the stutterers were ranked according to amount of disfluency. Under masking it appeared that the most and least disfluent stutterers experienced the greatest fluency improvement. This improvement in fluency tended to be associated with longer vowel duration, increased duration of vocal continuity, faster oral reading rate and a decrease in intensity. Theoretical implications of this study's findings were discussed.