[1] Univ Texas Austin, Dept Speech Language & Hearing Sci, Austin, TX 78712 USA
[2] Univ Wisconsin, Waisman Ctr, Madison, WI USA
[3] Northeastern Univ, Dept Commun Sci & Disorders, Boston, MA USA
[4] Univ Pretoria, Ctr Augmentat & Alternat Commun, Pretoria, South Africa
[5] Boston Childrens Hosp, Dept Otolaryngol & Commun Enhancement, Boston, MA USA