How ultrasound tongue imaging (UTI) works
Ultrasound is sound with a frequency higher than 20kHz. The ultrasound used in our ultrasound tongue imaging system has a frequency of 5MHz.
The tongue is a large flexible muscular organ that stretches from its root at the top of the throat to its tip, which can be protruded from the mouth. Most of the tongue’s mass is hidden from view, inside of the oral and pharyngeal cavities. The tongue is crucial to speech production: a large number of consonant and all vowel sounds are produced by modifying the shape of the tongue. Consonantal sounds are often produced by using the tongue to block or restrict air flow in the oral tract, while vowel sounds and sonorous consonants such as [j], [l], [ɹ] and [w] are produced by shaping pockets of air inside of the vocal tract so that these pockets of air resonate at specific frequency ranges.
Figure 1: A midsagittal MRI image of the vocal tract.