Communication aids are an aided AAC medium that can improve communication for those who otherwise experience difficulties with speaking. Voice output communication aids (VOCAs) provide speech output based on the user’s input and typically use speech synthesis technology.

VOCAs present a challenging design brief. Using technology to support face to face communication is a unique challenge that is further compounded by the fact that those accessing VOCAs may require alternative methods of control and/or representation of language. VOCAs are consequently often perceived as slow and ineffectual by those who use them.

Design thus offers a considerable potential role in improving the outcomes of VOCA use. This thesis collates a body of work related to the design of VOCAs. The work described investigated different aspects of VOCA design and this commentary explores how these aspects of design impact on the usability of VOCAs.

Five publications by the author and a commentary are presented with the aim of demonstrating that the body of work is substantial, coherent, and impactful. The included publications were derived from a number of projects investigating and developing VOCAs and assistive technologies in which the author was involved.