Chapter 2 explains the phonetic and phonological background of sibilant analysis.It first establishes a definition of the phoneme and then continues to describe the sounds involved based on an articulatory point of view. These are then connected to acoustic theories of speech production that illustrate how prototypical articulatory gestures create the resulting sound waves that are perceived as phonemes. It specifically explains how source filter theory and turbulence are important to the production of sibilants. It then illustrates how the acoustic output created can be quantified and classified based on characteristics such as spectral mean, skewness, and kurtosis of the speech signal.

The chapter then moves on to suprasegmental theories and fundamentals of /str/-retraction research. It explains how exemplar models of the mental lexicon are suitable to describe the sound change at hand. It then briefly illustrates the uniqueness of triple-consonant clusters in English. As important processes in this sound change, coarticulation and assimilation are then differentiated.

Individual speech sounds are modified by the phonetic environment in which they are found in connected speech. In this book, the term accommodation is used generically for any and all articulatory modifications that arise from the phonetic environment. The term assimilation is used for accommodation that crosses phonemic boundaries, and coarticulation is used for sub-phonemic accommodations. Accommodation occurs not due to laziness, but through these forces: (1) the fundamental constraints on producing a number of segments in rapid, connected succession, and (2) the efficiency of speech production – not producing gestures, or extending gestures beyond what is required for the production of highly intelligible speech. Accommodations might be informally called shortcuts, and some shortcuts are required by physical constraints and some are not; others are required by the grammatical rules of the language in question, defined by language-specific rules.

When speech sounds are produced, articulatory movements for one sound overlap with those of the surrounding sounds, generating articulatory and acoustic signals that at any point in time are informative about two or more sounds, not just one. This process of intermingling of information about several speech sounds in the articulatory and acoustic signals is called coarticulation. This chapter synthesises theories and experimental findings of the last century on the nature of coarticulation, and shows how our modern understanding of this complex process is deeply rooted in theories that have evolved over decades due to novel experimental findings as well as critique from competing theories. After discussion of our current understanding of coarticulation, some suggestions for initiating students into the surprising effects of coarticulation are introduced.