Acoustic comparison of rhotic acquisition in biofeedback versus motor-based treatment for residual speech sound disorder

Around 2%-5% of speakers aged 8 and up experience Residual Speech Sound Disorder (RSSD), which can persist despite years of intervention and may negatively impact a child’s social and academic outcomes. Previous studies have investigated visual biofeedback as an alternative intervention for RSSD affecting the English rhotic /ɹ/. These studies have been inconclusive because of study design limitations and small sample sizes. Furthermore, most previous studies have focused on generalization gains at the end of a period of treatment, but theories of motor learning suggest that any differences between biofeedback and treatment will be most apparent early in treatment. Data for this study were sourced from an ongoing project, Correcting Residual Errors with Spectral, ULtrasound, Traditional Speech therapy Randomized Controlled Trial (C-RESULTS RCT), which aims to compare biofeedback and non-biofeedback interventions for RSSD affecting /ɹ/ using a well-powered randomized controlled trial design. In this study, eighty children with /ɹ/ misarticulation were randomized to receive traditional motor-based treatment or biofeedback treatment (with ultrasound and visual-acoustic biofeedback subtypes). We hypothesized that acoustic measures of /ɹ/ production accuracy would show faster gains in the first three intervention sessions (acquisition phase) for children who received biofeedback rather than motor-based treatment.