Head-probe stabilisation in ultrasound tongue imaging using a headset to permit natural head movement

Translation and rotation movements of an ultrasound probe relative to the speaker’s head induce error. We examine one means of reducing such errors, the headset stabilising system made by Articulate Instruments Ltd., using a Vicon 612 3D motion analysis system during and between episodes of speech. Probe movements relative to the head of the speaker were derived. The headset restricted unwanted movement to the midsagittal plane even though a speaker was free to move the head naturally during utterances. Stressed low vowels moved the probe dynamically within this plane by as much as 10mm in extreme cases before it returned to near its original position. Long-term slippage ranged from 1.4mm to 2.9mm and is within acceptable limits. 1