This paper describes two electromagnetic midsagittal articulometer (EMMA) systems that were developed for transducing articulatory movements during speech production. Alternating magnetic fields are generated by transmitter coils that are mounted in an assembly that fits on the head of a speaker. The fields induce alternating voltages in a number of small transducer coils that are attached to articulators in the midline plane, inside and outside the vocal tract. The transducers are connected by fine lead wires to receiver electronics whose output voltages are processed to yield measures of transducer locations as a function of time. Measurement error can arise with this method, because as the articulators move and change shape, the transducers can undergo a varying amount of rotational misalignment with respect to the transmitter axes; both systems are designed to correct for transducer misalignment. For this purpose, one system uses two transmitters and biaxial transducers; the other uses three transmitters and single-axis transducers. The systems have been compared with one another in terms of their performance, human subjects compatibility, and ease of use. Both systems can produce useful midsagittal-plane data on articular movement, and each one has a specific set of advantages and limitations. (Two commercially available systems are also described briefly for comparison purposes). If appropriate experimental controls are used, the three-transmitter system is preferable for practical reasons.

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This study addresses the hypothesis that the more accurately a speaker discriminates a vowel contrast, the more distinctly the speaker produces that contrast. Measures of speech production and perception were collected from 19 young adult speakers of American English. In the production experiment, speakers repeated the words cod, cud, who'd, and hood in a carrier phrase at normal, clear, and fast rates. Articulatory movements and the associated acoustic signal were recorded, yielding measures of contrast distance between /Ä/ and /#/ and between /u/ and /*/. In the discrimination experiment, sets of seven natural-sounding stimuli ranging from cod to cud and who'd to hood were synthesized, based on productions by one male and one female speaker. The continua were then presented to each of the 19 speakers in labeling and discrimination tasks. Consistent with the hypothesis, speakers with discrimination scores above the median produced greater acoustic contrasts than speakers with discrimination scores at or below the median. Such a relation between speech production and perception is compatible with a model of speech production in which articulatory movements for vowels are planned primarily in auditory space.