Although standard speech quality measures such as PESQ do not work well for synthetic speech, specially constructed methods do work to some extent.
Mayo et al: Multidimensional scaling of listener responses to synthetic speech
Multi-dimensional scaling is a way to uncover the different perceptual dimensions that listeners use, when rating synthetic speech.
Clark et al: Multisyn: Open-domain unit selection for the Festival speech synthesis system
A description of the implementation and evaluation of Festival’s unit selection engine, called Multisyn.
Handbook of phonetic sciences – Ch 20 – Intro to Signal Processing for Speech
Written for a non-technical audience, this gently introduces some key concepts in speech signal processing.
This is the new version. Still under construction.