Effect of frequency-altered feedback on stuttering frequency at normal and fast speech rates.

The purpose of this study was to determine the effect of the magnitude and direction of the frequency shift of frequency-altered auditory feedback (FAF) on stuttering frequency at both normal and fast speech rates. Twelve adult male and 2 adult female subjects who stutter read 10 different passages at either a normal or fast speech rate under nonaltered auditory feedback (NAF) and each of four FAF conditions in which the feedback signal was shifted: up one-half octave; up one octave; down one-half octave; and down one octave. Mean stuttering frequency for NAF was significantly higher than mean stuttering frequencies for all FAF conditions (p < 0.05). There were no statistically significant differences between the FAF conditions (p > 0.05). Subjects exhibited significantly more disfluencies under the fast speech rate condition relative to the normal speech rate condition. Future research should examine the relationship between frequency shifts of less than one-half octave and stuttering amelioration.