Preliminary Investigation of Four Voice Therapy Concepts in a Single-Subject Design with Four Professional Teachers

The Global Voice Prevention and Therapy Model (GVPTM) with the Estill Voice Model (EVM) involves four concepts: 1) training multiple new voice targets to meet all the vocal demands of the client, 2) using an integrated implicit-explicit instructional approach, 3) switching between voice targets, and 4) facilitating voice practice in a bottom-up speech hierarchy. As a preliminary investigation into the four concepts, the current study compared the GVPTM with EVM to a modified version of the GVPTM (MGVPTM) with EVM that eliminated concepts 1 (only one new resonant voice was trained) and 3 (no switching between voice targets) and kept concepts 2 and 4.

Four professional teachers were randomized into one of two conditions in a single-subject design counterbalanced with alternating treatments and baselines (ie, A₁BA₂CA₃ or A₁CA₂BA₃). In condition 1 (A₁BA₂CA₃), the GVPTM was first followed by MGVPTM. In condition 2 (A₁CA₂BA₃), the MGVPTM was first followed by the GVPTM. Baseline measures included fundamental frequency (f_o), participant self-ratings of overall voice quality, roughness, and strain, the Voice Handicap Index (VHI)-10, Vocal Fatigue Index (VFI), survey questions, and answers to questions via an exit interview.

The results indicated significant differences for f_o and self-ratings of overall vocal quality, roughness, and strain from pre to post for the GVPTM and MGVPTM. VHI-10 and VFI factors 1, 2, and 3 yielded no differences from pre to post. Overall, the participants viewed all four concepts in the GVPTM favorably and suggested it was limiting to learn only one new resonant voice with no switching between voice targets in the MGVPTM.

Speech-language pathologists may consider using all four concepts in voice therapy sessions represented via targets, ingredients, and mechanisms of action of the Rehabilitation Treatment Specification System.