Voice Onset Time and Burst Duration in the Fluent and Dysfluent Speech of Persons Who Stutter

Stuttering is a speech disorder where there is a disruption in the flow of information. It may be due to poorly timed muscle activity during stuttering instances. Acoustic parameters such as voice onset time (VOT) and burst duration (BD) serve as a sensitive indicator of timing control during speech production. It can indicate the improper timing between laryngeal and articulatory muscle activity. Understanding the VOT and BD during fluent and dysfluent production of the same individual may provide an insight into the physiological and motor bases of stuttering. Fifteen Kannada speaking adult males who stutter, aged between 19 and 30 years participated in the study. The natural speech samples were elicited through a story narration task and was audio-video recorded in a sound-treated room. Stops consonants containing bilabials (/p/ and /b/) and velars (/k/ and /g/) were extracted from dysfluent and fluent productions. VOT and BD were measured using PRAAT software. Statistical analysis was performed using paired t-test to compare between fluent and dysfluent productions. Dysfluent productions had significantly longer VOT and BD for velars and BD for bilabials (p < 0.001). However, there weren’t any significant differences between dysfluent and fluent production of /p/ (p = 0.338) and /b/ (p = 0.277). Two participants also exhibited voicing errors. The increase in VOT and BD may be attributed to the instability in laryngeal and articulatory timing. Results of this study support the temporal disorganization in speech-motor control. Acoustic measures help reveal subtle issues, guide therapy targeting coordination, and track progress.