Formant frequency fluctuation in stuttering and nonstuttering adults

Inferences were made regarding the vocal tract stability of stutterers' and nonstutterers' fluent speech through the examination of formant frequency fluctuation (FFF). Fifteen adult males served as subjects comprising separate groups of untreated stutterers, stutterers en rolled in a fluency-shaping treatment program, and nonstuttering controls. The steady-state portion of formant 2 (F2) was examined in the production of various CVC tokens and evaluated by examining the absolute Hz difference in F2 across consecutive glottal periods. Results of the acoustic analysis indicated a trend in FFF across the three groups. The untreated stutterers displayed the greatest FFF, followed by the control group, with the treated stutterers displaying the most F2 stability. Discussion focuses on the vocal tract stability displayed by each group, as well as the influence of a fluency-shaping treatment program to achieve perceptually fluent speech.