The Effects of Three Levels of Auditory Masking on Selected Vocal Characteristics and the Frequency of Disfluency of Adult Stutterers

Abstract

This study was designed to test the hypothesis that the growth function of the masking effect in stuttering behavior is promoted by systematic increases in vocal intensity. Sixteen normal-hearing adult stutterers read aloud in four conditions (quiet and 10-, 50-, and 90-dB sensation levels of continuous white noise). The oral readings were tape recorded. The recorded data were analyzed later to quantify subjects' vocal intensity, stuttering frequency, and reading time in each condition. The results showed that under various levels of masking, there is an inverse relationship between vocal intensity and stuttering frequency. The results of reading time comparisons between conditions were affected by the absolute frequency of stuttering in quiet or the magnitude of the masking effect or both. Finally, changes in vocal intensity were translated into physiological terms and then interpreted in light of how they might promote fluency and reduce stuttering.