Brief description

In Electromagnetic Articulometry (EMA), an electromagnetic field is used to track movements of small receiver coils glued on the speech articulators. Three (in two-dimensional EMA) or six (in three-dimensional EMA) transmitter coils are fixed on a cubic plastic apparatus surrounding the speaker's head. The transmitter coils produce alternating magnetic fields at different frequencies in the range of about 10 kHz. The fields from the transmitter coils pass through the receiver coils and generate an electric signal. The voltage of this signal is related to the distance and orientation of the receiver relative to the transmitter coils. This relationship is used to calculate the position of the receivers as a function of time. The voltages in the receiver coils are captured at a sampling rate of 200 Hz. Audio data are also collected in parallel with the articulatory data.

Sources on EMA

Perkell, J. S., Cohen, M. H., Svirsky, M. A., Matthies, M. L., Garabieta, I., & M. T. Jackson. 1992. Electromagnetic midsagittal articulometer systems for transducing speech articulatory movements. Journal of the Acoustical Society of America 92, 3078-3096.

Hoole, P., Zierdt, A. & C. Geng. 2003. Beyond 2D in articulatory data acquisition and analysis. In M. Solé, D. Recasens & J. Romero (eds.), Proceedings of the 15th International Congress of Phonetic Sciences, 265-268. Barcelona, Spain.

See Philip Hoole's 5D EMA examples here.

Sample data

Articulatory movements in the Hungarian word zafír-ban 'sapphire-DATIVE' acquired with the Electromagnetometer. The top panel represents the acoustic waveform, with broad phonemic IPA transcription of the segments in this word. The bottom three panels represent the vertical (solid curve) and horizontal (dashed curve) position of the receivers attached on the tongue dorsum (TD), tongue body (TB), and lower lip (LL). As the tongue body smoothly moves from vowel to vowel in this word, the TB, TD receivers can be seen to trace a bell-shaped trajectory from a retracted position for the first back vowel with low horizontal values of TB and TD, shown by the first valley in the dashed curves, to an advanced position for the second, front vowel, with higher horizontal positions for TB and TD, shown by the peaks in the dashed curves, and back to a retracted position of the final back vowel, shown by the second valley in the dashed curves.



Source: Gafos, A., Stefan Benus. 2006. Dynamics of phonological cognition. Cognitive Science 30(5), 905-943.