Challenges in evaluating the intelligibility of text-to-speech

Text-to-speech (TTS) technology imposes different constraints on intelligibility than those sufficient for the evaluation of other speech communication systems. For example, the newly revised standard S.2-2009 explicitly excludes TTS from the speech communication systems it covers. Since there is no current standard appropriate for evaluating TTS intelligibility, the ASA Standards Bioacoustics (S3) working group on Text-to-Speech Technology (WG91) was formed with the initial goal of developing such standard. We describe several ways in which standard methods of testing speech intelligibility are unsuitable for TTS technology and outline our approach to overcoming these limitations. We present an overview of our proposed standard, which is currently nearing its final draft stages.