Accuracy assessment of two electromagnetic articulographs: NDI Wave and NDI Vox

Teja Rebernik*, Jidde Jacobi, Mark Tiede, Martijn Wieling

*Bijbehorende auteur voor dit werk

    OnderzoeksoutputAcademicpeer review

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    Samenvatting

    Purpose
    This study compares two electromagnetic articulographs manufactured by Northern Digital, Inc.: the NDI Wave System (from 2008) and the NDI Vox-EMA System (from 2020).

    Method
    Four experiments were completed: (a) comparison of statically positioned sensors, (b) tracking dynamic movements of sensors manipulated using a motor-driven LEGO apparatus, (c) tracking small and large movements of sensors mounted in a rigid bar manipulated by hand, and (d) tracking movements of sensors rotated on a circular disc. We assessed spatial variability for statically positioned sensors, variability in the transduced Euclidean distances between sensor pairs, and missing data rates. For sensors tracking circular movements, we compared the fit between fitted ideal circles and actual trajectories.

    Results
    The average sensor pair tracking error (i.e., the standard deviation of the Euclidean distances) was 1.37 mm for the WAVE and 0.12 mm for the VOX during automated trials at the fastest speed, and 0.35 mm for the WAVE and 0.14 mm for the VOX during the tracking of large manual movements. The average standard deviation of the fitted circle radii charted by manual circular disc movements was 0.72 mm for the WAVE sensors and 0.14 mm for the VOX sensors. There was no significant difference between the WAVE and the VOX in the number of missing frames.

    Conclusions
    In general, the VOX system significantly outperformed the WAVE on measures of both static precision and dynamic accuracy (automated and manual). For both systems, positional precision and spatial variability were influenced by the sensors' position relative to the field generator unit (worse when further away).
    Originele taal-2English
    Pagina's (van-tot)2637-2667
    Aantal pagina's31
    TijdschriftJournal of Speech, Language and Hearing Research
    Volume64
    Nummer van het tijdschrift7
    DOI's
    StatusPublished - jul.-2021

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