Hands-On Natural Language Processing with Python

Naturalness versus intelligibility

The quality of a TTS system is traditionally assessed through two criteria: naturalness and intelligibility. This is motivated by the fact that people are not only sensitive to what the audio content is, but also to how that content is delivered. Basically, we want a TTS system that can produce clear audio content in a human-like way. More precisely, intelligibility is about the audio quality or cleanness, and naturalness is about communicating the message with the proper pronunciation, timing, and range of emotions.

With a highly intelligible system, it is effortless for the user to distinguish between different words. On the other hand, when intelligibility is low, some words might be confused with others ...