Speech synthesis applications have become an ubiquity, in navigation

systems, digital assistants or as screen or audio book

readers. Despite their impact on the acceptability of the systems

in which they are embedded, and despite the fact that different

applications probably need different types of TTS voices,

TTS evaluation is still largely treated as an isolated problem.

Even though there is strong agreement among researchers that

the mainstream approaches to Text-to-Speech (TTS) evaluation

are often insufficient and may even be misleading, there exist

few clear-cut suggestions as to (1) how TTS evaluations may

be realistically improved on a large scale, and (2) how such improvements

may lead to an informed feedback for system developers

and, ultimately, better systems relying on TTS. This paper

reviews the current state-of-the-art in TTS evaluation, and suggests

a novel user-centered research program for this area.