Frequency modulated feedback of ones own voice can cause dysfluence of speech

Delayed auditory feedback (DAF) can cause speech dysfluency (e.g., stuttering) in healthy normal subjects. In previous studies, feedback frequency was changed linearly or to a constant value in FAF. In this study, we introduce frequency‐modulated feedback of pitch in a sine‐wave manner. The modulation depth of pitch (F0) of auditory feedback voice was six semitones, and the modulation frequencies of sinewaves were set at 0.05, 0.1, 0.5, 0.9, 2, 4, 6, 8, 10, 12, 14, and 16 Hz. In addition to the FAF experiment, we conducted DAF experiments with delay times of 50, 200, and 400 ms. Participants (18 Chinese and 18 Japanese) were instructed to read sentences as they listened to the altered feedback voice through a headphone under each condition. Speech dysfluency was apparent under all FAF and DAF conditions for both groups. Only when the modulation frequency was 14 Hz did Chinese subjects show significantly larger disturbance than Japanese in FAF. A significant greater disturbance of Chinese in DAF was observed when the delay time was 50 ms. These results indicate that frequency modulation can cause speech dysfluency, as does DAF. [Work supported by the 21st century COE (Center of Excellence) Program.]