Numerical instabilities and three-dimensional electromagnetic articulography.

The AG500 electromagnetic articulograph is widely used to reconstruct the movements of the articulatory organs. Nevertheless, some anomalies in its performance have been observed. It is well known that accuracy of the device is affected by electromagnetic interference and possible hardware failures or damage to the sensors. In this study, after eliminating any hardware or electromagnetic source of disturbance, a set of trials was carried out. The tests prove that anomalies in sensor position tracking are systematic in certain regions within the recording volume and, more importantly, show a specific pattern that can be clearly attributed to a wrong convergence of the calculation method.