Design and construction of an alternating magnetic field system for transducing articulatory movements in the midsagittal plane

Abstract

A system for tracking multiple articulatory movements in the midsagittal plane has been designed and prototyped. The system uses alternating magnetic fields generated by two transmitter coils which are mounted in a magnetically transparent assembly that fits on the subject's head. Receiver transducers consist of small (4 × 4 × 2 mm) biaxial inductors which are attached to articulatory structures and have fine lead wires that are connected to demodulating circuits. The biaxial transducer design provides measurements that are independent of transducer tilt [J. S. Perkell, J. Acoust. Soc. Am. Suppl. 1 71, S32 (1982)]. Movements of as many as seven points inside and outside the vocal tract can be tracked, with two additional fixed points for use as a maxillary frame of reference. The measurement area is 150 × 150 mm, allowing for coverage from the rear wall of the pharynx to the lips and the bridge of the nose to the base of the tongue. Output voltages are low‐pass filtered and digitized. Algorithms have been developed for conversion of digitized voltages to Cartesian coordinates. Output can be displayed as X and Y coordinates versus time or X versus Y trajectories. [Work supported by NIH Grant NS04332.]