5 - The vocal tract

Summary

Overview

This chapter begins to engage with a distinction that will be increasingly important in subsequent chapters, between language and speech. Language is something that happens at least in part in our brains, and might in some respects be controlled by our genes; we return to this in the next chapter. However, the primary modality of most language users is speech; it is the main way we externalise our knowledge of language and make use of it in the world. In this chapter, we outline the anatomy and physiology of human speech production, considering evidence from the biological comparative method to assess which aspects might be specific to humans and when these might have developed in our evolutionary history. We also, however, raise the question of modalities other than speech, and consider the possibility that the origin of language may lie in gesture as well as sound.

Producing speech sounds

Students learning acoustic phonetics used to be told to imagine the human vocal tract as a tube of uniform cross-section, approximately 15 centimetres long. However, this highly idealised description factors out most of what really matters for speech production. If our vocal tracts were really just single tubes, we would not only look rather different, but would not be able to produce some of the most important sounds of human languages.