Perturbation and compensation in speech acoustics using a jaw-coupled robot

Abstract

Observations were made in three speakers of compensation in formant trajectories in response to jaw perturbations during utterances with the general form /siyCVd/, as in ‘‘see red.’’ Custom dental prostheses were used to help immobilize the head (upper jaw) and couple a computer-controlled robotic device (lower jaw). A 3-Newton perturbation force was applied to the jaw during one out of every five repetitions, selected at random, with half of the perturbations applied downward and half upward. Perturbations were triggered from jaw opening (for CV) exceeding a threshold relative to clench position. Audio (at 10 kHz) and jaw position (at 1 kHz) were recorded concurrently. Individual tokens were extracted using the perturbation threshold for alignment. Formants computed over these intervals show initial deviation from control trajectories and then compensation that begins 60–90 ms after perturbation. Since jaw position does not recover its unperturbed trajectory, compensation presumably is effected through modified tongue movements. The observed behavior is compatible with the function of the DIVA model of speech motor planning, in which corrective motor commands are computed in response to errors between anticipated and produced sensory (auditory and somatosensory) consequences. [Research supported by NIDCD.]