Focus on the concepts and diagrams, and don't worry about understanding the maths too much.
in Paul Taylor “Text-to-speech synthesis”, 2009, Cambridge University Press, Cambridge, ISBN 0521899273
Taylor - Section 10.1 - Analogue signals
It's easier to start by understanding physical signals - which are analogue - before we then approximate them digitally.
Taylor - Section 10.2 - Digital signals
Going digital involves approximations in the way an original analogue signal is represented.
This is the new version. Still under construction.