  Statistical TTS systems that directly predict the speech waveform have
recently reported improvements in synthesis quality. This investigation
evaluates Amazon's statistical speech waveform synthesis (SSWS) system. An
in-depth evaluation of SSWS is conducted across a number of domains to better
understand the consistency in quality. The results of this evaluation are
validated by repeating the procedure on a separate group of testers. Finally,
an analysis of the nature of speech errors of SSWS compared to hybrid unit
selection synthesis is conducted to identify the strengths and weaknesses of
SSWS. Having a deeper insight into SSWS allows us to better define the focus of
future work to improve this new technology.
