This paper attempts to make certain qualitative differences between stutterers and non-stutterers clear by means of acoustic analysis. Previous studies have highlighted three areas of relevance to this study. The first is that breath control while speaking is difficult for stutterers. Secondly, the beginning of words are particularly challenging for stutterers. Finally, even without treatment, stutterers have on average an 80% chance of naturally recovering. The author collected data from 61 stutterers and the same number of non-stutterers, by recording their voices and analyzing them acoustically, such as for shimmer parameters. The conclusions are as follows. Preschool children (two to six years) and adults (twenty years or above) who stutter registered a statistically significant increase in score for Amplitude Perturbation Quotient (APQ) and Shimmer Parameter (SP) than non-stutterers of the same age range. This data suggests that stutterers have something wrong with their respiratory controls. On the other hand, for children of 7〜9 years old, APQ and SP scores were not statistically different between stutterers and non-stutterers. This suggests that the second stage of laryngeal development is correlated to the process of natural recovery. Also stutterers' problem of disfluency would appear to originate in the motor speech center in the brain.
