The effects of delayed auditory feedback and masking on the fundamental frequency of stutterers and nonstutterers.

This investigation determined if fluency of the reader or type of auditory feedback changed characteristics of fundamental frequency or duration in oral reading by stutterers or nonstutterers. Mingographic tracings were made of sentences excerpted from tape recordings of paragraphs read by 15 adult male stutterers and 15 adult male nonstutterers in three conditions of feedback: normal auditory feedback (under earphones), delayed auditory feedback (0.14 sec delay), and masking (90 dB SPL). The data included 15 measures of fundamental frequency and two measures of duration. Stutterers read sentences in greater total time and with more downward inflections than nonstutterers. Comparison of the delayed auditory feedback (DAF) conditions with the normal auditory feedback (NAF) condition showed that the numbers of total, upward, and downward inflections and upward pitch shifts increased under DAF. In the DAF condition, average rates of upward and downward inflections decreased, and mean and median fundamental frequencies and total time increased. The only changes from the NAF to the masking condition were increases in mean and median fundamental frequencies.