Effects of delayed auditory feedback on the vocal time-reproduction

A study was conducted to propose an analytical method for assessing temporal interference of speech by delayed auditory feedback (DAF) quantitatively and in isolation. Fifteen native Japanese speakers, including 8 males and 7 females aged between 19-31 years participated in this experiment. Participants were seated comfortably on a chair in a sound attenuated chamber. They were instructed to produce a vowel /a/ with the same duration as a pre-presented tone and their voice was recorded with a microphone attached to headphones located approximately 5 cm from the participants' mouth. The voice was sent to a mixer, an audio recorder, and a delay machine. The voice sent to the delay machine was delayed by 200 ms and played back into the headphones after mixing with white masking noise from a noise generator. The delay under the DAF condition was configured at 200 ms, as it was well known that the 200 ms was the most disruptive delay on speech control.