Variance and Invariance

One of the most outstanding properties of speech in any language is the variability or lack of invariance in the production of sounds. Speech is highly variable. The sound phonemes in spoken language are mutable, influenced by speaker, by context, by speech rate, and by other factors. 

Variability is to be expected; it may even aid speech perception. In the face of variability, one of the more remarkable properties of the sound phonemes of the Dene languages is the consistency in their articulation across the languages, as can be seen in the data in the DSA. The patterns of variability that are found, in the voicing of obstruents, the lenition of fricatives, and habits of glottalization are remarkably consistent across the Dene languages in spite of the isolation of the communities from each other and their geographic dispersion. Some of these types of variations are types commonly found cross-linguistically, but some are quite specific to the Dene language family. 

Phoneticians look for the patterns in speech that mark the sounds and the sound contrasts of a language. Traditionally, sounds and contrasts have been classified in terms of feature sets, such as laryngeal features of voicing or aspiration, or manner features, such as fricative or sonorant. In reality, these features, while helpful and important, can be superficial, and may capture only quite general properties of a sound. These features may not adequately capture the nature of the contrasts that exist in a sound system of a language, or the variation present in them. 

This indicates that these patterns of phonetic detail in the articulation of these sounds are supported, or support, important infrastructural properties in the language. These are likely to be related to morphological structures and integrated into how speakers store and retrieve words efficiently.