Accuracy and Precision of a Custom Camera-Based System for 2-D and 3-D Motion Tracking During Speech and Nonspeech Motor Tasks PurposeStudying normal or disordered motor control requires accurate motion tracking of the effectors (e.g., orofacial structures). The cost of electromagnetic, optoelectronic, and ultrasound systems is prohibitive for many laboratories and limits clinical applications. For external movements (lips, jaw), video-based systems may be a viable alternative, provided that they offer high ... Research Note
Research Note  |   April 01, 2014
Accuracy and Precision of a Custom Camera-Based System for 2-D and 3-D Motion Tracking During Speech and Nonspeech Motor Tasks
 
Author Affiliations & Notes
  • Yongqiang Feng
    Key Laboratory of Speech Acoustics and Content Understanding, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China
  • Ludo Max
    University of Washington, Seattle, WA
    Haskins Laboratories, New Haven, CT
  • Disclosure:The authors have declared that no competing interests existed at the time of publication.
    Disclosure:The authors have declared that no competing interests existed at the time of publication.×
  • Correspondence to Yongqiang Feng: johnfengyq@yahoo.com.
  • Editor: Jody Kreiman
    Editor: Jody Kreiman×
  • Associate Editor: Kate Bunton
    Associate Editor: Kate Bunton×
Article Information
Research Issues, Methods & Evidence-Based Practice / Speech, Voice & Prosody / Speech
Research Note   |   April 01, 2014
Accuracy and Precision of a Custom Camera-Based System for 2-D and 3-D Motion Tracking During Speech and Nonspeech Motor Tasks
Journal of Speech, Language, and Hearing Research, April 2014, Vol. 57, 426-438. doi:10.1044/2014_JSLHR-S-13-0007
History: Received January 7, 2013 , Revised July 1, 2013 , Accepted November 6, 2013
 
Journal of Speech, Language, and Hearing Research, April 2014, Vol. 57, 426-438. doi:10.1044/2014_JSLHR-S-13-0007
History: Received January 7, 2013; Revised July 1, 2013; Accepted November 6, 2013
Web of Science® Times Cited: 4

PurposeStudying normal or disordered motor control requires accurate motion tracking of the effectors (e.g., orofacial structures). The cost of electromagnetic, optoelectronic, and ultrasound systems is prohibitive for many laboratories and limits clinical applications. For external movements (lips, jaw), video-based systems may be a viable alternative, provided that they offer high temporal resolution and submillimeter accuracy.

MethodThe authors examined the accuracy and precision of 2-D and 3-D data recorded with a system that combines consumer-grade digital cameras capturing 60, 120, or 240 frames per second (fps), retro-reflective markers, commercially available computer software (APAS, Ariel Dynamics), and a custom calibration device.

ResultsOverall root-mean-square error (RMSE) across tests was 0.15 mm for static tracking and 0.26 mm for dynamic tracking, with corresponding precision (SD) values of 0.11 and 0.19 mm, respectively. The effect of frame rate varied across conditions, but, generally, accuracy was reduced at 240 fps. The effect of marker size (3- vs. 6-mm diameter) was negligible at all frame rates for both 2-D and 3-D data.

ConclusionMotion tracking with consumer-grade digital cameras and the APAS software can achieve submillimeter accuracy at frame rates that are appropriate for kinematic analyses of lip/jaw movements for both research and clinical purposes.

Acknowledgments
This work was supported in part by National Institute on Deafness and Other Communication Disorders Grant R01DC007603 and Institute of Acoustics, Chinese Academy of Sciences Grant Y154221431. We thank Thomas J. Mealy for mechanical engineering support.
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