Indexing head movement during speech production using optical markers.

Optical marker tracking integrated with electromagnetic articulometry was used to assess the movement extent of various points on (a) forehead skin and (b) points on a head-mounted apparatus, relative to a fixed point just above the upper incisors, and to compare the accuracy of the two different approaches to indexing head position during speech production. Both methods can provide a satisfactory index of head position. If skin-affixed markers are used, a minimum of 4 is recommended. Locations for optimal marker placement are identified.