An evaluation of the aurora system as a flesh-point tracking tool for speech production research

Purpose: Northern Digital Instruments (NDI; Waterloo, Ontario, Canada) manufactures a commercially available magnetometer device called Aurora that features real-time display of sensor position tracked in 3 dimensions. To test its potential for speech production research, data were collected to assess the measurement accuracy and reliability of the system. Method: First, sensors affixed at a known distance on a rigid ruler were moved systematically through the measurement space. Second, sensors attached to the speech articulators of a human participant were tracked during various speech tasks. Results: In the ruler task, results showed mean distance errors of less than 1 mm, with some sensitivity to location within the measurement field. In the speech tasks, Euclidean distance between jaw-mounted sensors showed comparable accuracy; however, a high incidence of missing samples was observed, positively correlated with sensor velocity. Conclusions: The real-time positional feedback provided by the system makes it potentially useful in speech therapy applications. The overall missing data rate observed during speech tasks makes use of the system in its current form problematic for the quantitative measurement of speech articulator movements; however, NDI is actively working to improve the Aurora system for use in this context.