Objective
The Global Voice Prevention and Therapy Model (GVPTM) with the Estill Voice Model (EVM) incorporates four voice therapy concepts: (1) training multiple new voice targets, (2) using an integrated implicit–explicit instructional approach, (3) switching between voice targets, and (4) practicing within a bottom-up speech hierarchy. Two studies evaluated these concepts, defined by the Rehabilitation Treatment Specification System (RTSS), comparing the GVPTM to a modified version (MGVPTM, concepts 2 and 4 only) and to Conversation Training Therapy (CTT, concept 3 only) using an alternating-treatments single-subject design with multiple baselines.
Methods
Fourteen participants (eight professional and six student teachers), with and without voice complaints, completed two voice therapy approaches: GVPTM and MGVPTM or GVPTM and CTT. Order of approaches was counterbalanced with half the participants beginning with the GVPTM and the other half beginning with the other approach (e.g., MGVPTM or CTT). Outcome measures included fundamental frequency (f₀), self-ratings of overall vocal quality (OVQ), roughness (R), and strain (S), Voice Handicap Index-10, Vocal Fatigue Index, survey questions, and open-ended responses during exit interviews.
Results
In study 1, results indicated significant improvements in f₀ and self-ratings of OVQ, R, and S from pre to post for the GVPTM and MGVPTM. Participants favored all four voice therapy concepts and found the MGVPTM limiting due to learning only one new resonant voice without switching between voice targets. In study 2, for teachers with voice complaints, the GVPTM improved f₀ and self-ratings of OVQ, R, and S, while CTT did not. For teachers without voice complaints, both the GVPTM and CTT were successful in improving f₀ and self-ratings of OVQ, R, and S. Teachers with voice complaints preferred the GVPTM over CTT, while teachers without voice complaints indicated no clear preference.
Conclusions
Findings support the use of all four voice therapy concepts embedded in the GVPTM. The GVPTM was more effective and preferred over the MGVPTM and CTT, especially for teachers with voice complaints, reinforcing the value of training multiple new voice targets, using an implicit-explicit integrated instructional approach, switching between voice targets, and facilitating a bottom-up speech hierarchy.