Imagine a child trying to say a tricky sound in a new word they have never practiced before. This study looked at whether giving them a visual tool, like an ultrasound or visual-acoustic display, could help. The participants were 108 children between 9 and 15 years old who had trouble with the American English /ʒ/ sound. They received either standard motor-based treatment or that same treatment plus visual biofeedback.
The group using visual biofeedback showed significantly greater improvement in using the sound correctly for words they had not practiced. Interestingly, the ultrasound version seemed to work even better than the visual-acoustic version in a specific sub-analysis. No safety issues were reported, and no children stopped the treatment early due to side effects.
Adding these visual tools can increase the rate of accurate production for untreated words. However, the effect of ultrasound versus visual-acoustic biofeedback was strongest at just one treatment site. This means we need more research from different places before we know if this approach works everywhere.