ATR Human Information Processing Res. Labs., 2-2 Hikaridai Seika-cho, Soraku-gun, Kyoto, 619-02 Japan
A rapid interaction between auditory perception and speech production has been found using the technique of transformed auditory feedback with fundamental frequency perturbation as the transformation. The technique of transformed auditory feedback has been developed to investigate the role of auditory perception in speech production under natural conditions. The basic idea of the method is to keep the disturbance of normal speech production processes to a minimum, while allowing interactions between speech production and auditory perception to be detectable. In the first experiment, subjects were instructed to sustain the Japanese vowel /a/ with a constant pitch. The phonated vowel was frequency modulated using sinusoids of 2- to 7-Hz range and fedback diotically via headphones. The modulation depth was 200 cent from peak to peak. The results indicate that there is a phase-locking effect in the fundamental frequency of the produced speech. In a second experiment, a correlation analysis using a pseudo-random signal as a modulator revealed that the reaction to fundamental frequency perturbation is corrective and that its latency ranges from 100 to 200 ms. Its relation with the auditory-laryngeal reflex will be discussed.