An important technique used widely in NLP. In TTS, it can be applied to tasks such as detecting and expanding non-standard words.
Holmes & Holmes – Chapter 5 – Message synthesis from stored human speech components
Pitch-synchronous overlap-and-add (PSOLA) remains a key technique in speech signal processing.
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.
Ladefoged (Elements) – Chapter 8 – Resonances of the vocal tract
A more detailed look at how resonance occurs in the vocal tract, and how that can be used to explain the sound quality (e.g. formant frequencies) of vowel sounds.
Ladefoged (Elements) – Chapter 7 – The production of speech
Some phonetics at last, and a first encounter with the source-filter model of speech.
Ladefoged (Elements) – Chapter 6 – Hearing
Some understanding of human hearing will be helpful for engineering suitable features to extract from the waveform for automatic speech recognition.
Ladefoged (Elements) – Chapter 5 – Resonance
Now we turn to speech production, and resonance is how the vocal tract shapes the quality of sound, to produce different vowels, for example.
Ladefoged (Elements) – Chapter 4 – Wave analysis
The waveform is rarely the best representation for analysis of sound, and this is an intuitive introduction to why.
Ladefoged (Elements) – Chapter 3 – Quality
A general term for aspects of sound other than loudness and pitch. Different vowels, for example, have a different quality of sound.
Ladefoged (Elements) – Chapter 2 – Loudness and pitch
These are perceptual phenomena that relate to physical properties of sound.
Ladefoged (Elements) – Chapter 1 – Sound waves
Very brief, but a reasonable place to start if you have no idea what sound is.