Use of an alternating magnetic field device to track midsagittal plane movements of multiple points inside the vocal tract
Joseph S. Perkell, Daisuke Oka · The Journal of the Acoustical Society of America · 1980
A three-channel magnetic field ranging device has been constructed incorporating previously-used principles [Hixon, J. Acoust. Soc. Am. 49, 603–606, (1971); van der Giet, J. Acoust. Soc. Am. 61, 1072–1076, (1977)]. Two large transmitting coils, each excited by a sinusoidal signal at a different frequency, are mounted on a helmet, above the forehead and below the occiput. Extremely small transducer-receivers consist of inductors mounted on a base with lead wires attached. The transducers are attached to the structures of interest and leads are brought out of the corner of the mouth. The magnetically induced signal in each transducer is demodulated to produce voltages which are related to distances between transmitters and transducer, allowing for spatial localization by triangulation. In spite of technical problems which remain to be resolved, the potential usefulness of such a device is indicated by preliminary results of a repetition experiment: The positioning of points on the tongue surface appears more variable in the direction parallel to the vocal tract midline at the place of constriction for point vowels than in the acoustically more critical direction, perpendicular to the midline. [Research supported by NIH Grant No. NS 04332.]