Speech physiology consists of the articulatory structures, including the respiratory system, the larynx and various vocal tract articulators, plus the sensory organs, which provide auditory, somatosensory and visual inputs that map the feature space in which speech is produced and perceived. In this chapter the focus is on the neurophysiology of the articulatory structures. The acoustic characteristics of speech sounds are determined by changes in the length and tension of muscles, coordinated, at the lowest level, by interlinked clusters of motor neurons and interneurons in the brainstem which are themselves directed by excitation from cortical and midbrain structures. This chapter provides a brief foundation to these systems and structures, taking a functional perspective. The progressive nature of research into the anatomy and physiology of speech continues to generate new discoveries, and advances in modelling and mapping of biomechanical and neural control promise new avenues for phonetic research.

The observation and measurement of the movement of the organs of the vocal tract during speech is relevant for the understanding of phonetic phenomena, from descriptions of under-documented languages and cross-linguistic comparison of speech sound production, to investigations of factors impacting speech motor planning, and to testing models of the relationship between the vocal tract and acoustics. This chapter describes the most commonly used methods for measuring or recording the position and movements of the organs that make up the vocal tract during speech. Techniques discussed in this chapter include direct vocal tract imaging (e.g. magnetic resonance imaging (MRI), laryngoscopy, ultrasound imaging), articulatory point tracking (e.g. X-ray microbeam tracking (XRMB), electromagnetic articulography (EMA), Velotrace), and indirect measures of articulator movement (e.g. electroglottography (EGG), airflow and air pressure measures, static palatography and electropalatography (EPG)). These methods vary in a number of respects. This chapter discusses advantages and drawbacks of each method described, as well as factors relevant to researchers during the planning stages of a study.