Vincent L. Gracco
Haskins Labs., 270 Crown St., New Haven, CT 06511
Dorothy Ross
City University of New York
Joseph Kalinowski
Andrew Stuart
Dalhousie University
The influence of auditory information on the control of speech movements was investigated. The subjects acoustic signal was directed through a digital signal processor and feedback to the subject through a set of insert earphones. Experimental manipulation of the subjects auditory feedback included elevating the sidetone an octave and the introduction of a delay (100--150 ms). Two-dimensional motion of the lips, the mandible, and front and rear of the tongue were obtained electromagnetically during repetitions of single syllables, phrases, and short sentences. Kinematic measures were obtained for the normal auditory condition and the two experimental conditions. Modulation of the subjects feedback had pronounced effects on the temporal properties of the movements with rate being the most salient. Delaying the auditory feedback slowed down speaking rate while frequency shifting increased speaking rate. Articulatory changes were generally consistent with the changes in speaking rate. Changes were also noted in the subjects fundamental frequency. In contrast, formant frequencies were generally unaffected by the distorted auditory signal. The results will be discussed with regard to the auditory contribution to sensorimotor control of vocal tract actions and the characteristics of the underlying vocal tract targets.