Evidence of laryngeal blocks in acoustic analysis of stuttered speech.

Abstract

Stuttered speech is characterized by the presence of speech blocks. Little is known on what causes blocks. These blocks typically occur on onset segments of a syllable regardless of the number of syllables in the stuttered word. Blocks on voiced and voiceless stops often result in part word repetitions (e.g., c c c car), while fricatives and other + continuant sounds will be prolonged. Therefore, the manner of sound production plays a role in identifying the types of blocks that will occur. Preliminary acoustic analysis of the speech of one subject with severe stuttering reveals that blocks occurring on voiced +continuant segments are prolonged; however, there is partial or complete devoicing of the voiced segment associated with the block. Devoicing is evident in the spectrogram by the absence of voicing bar and fundamental frequency. Sonorant segments can be identified by their resonant frequencies. This pattern was found in both spontaneous and read speech. The presence of resonant frequencies in the absence of a fundamental frequency indicates a block at the region of the vocal folds. A follow up to this study analyzing simultaneous EGG and acoustic recordings to look at the glottal cycle during stuttered blocks is required.