Effects of stuttering on fundamental frequency

The purpose of this study was to systematically investigate quantitative fundamental frequency measures prior to moments of stuttering, and relate these measures to the severity and type of stuttering. A repeated readings adaptation procedure was employed to acquire samples of the stuttered and identical fluent speech of stutterers. Thirty-six utterance pairs were classified by type of stuttering (absence of phonation, prolongation, or repetition). A fundamental frequency meter was sampled by a microprocessor computer system at a rate of 256 samples/1.024 sec. Four temporal periods (each 256 msec) preceding the stuttering block were compared with the same periods in a fluently produced sample of similar speech. The analyses revealed differences relative to mean fundamental frequency, variation around the mean fundamental frequency, and the number of voiced data points contained within each temporal segment. The results of this study confirm the existence of acoustic changes in the vocal production of stutterers prior to overt blocks. These changes relate to the type of block that follows. Individual variations that emphasize the need for analyses of within subject differences were found.