From Airstream to Utterance: Vowels, Consonants, and Suprasegmentals Speech production relies on the lungs generating an airstream, the larynx shaping it through phonation, and the vocal tract’s active articulators modulating it into vowels and consonants. All languages use an outward (egressive) pulmonic airstream, while inward pulmonic flow is exceptional. Other mechanisms include glottalic airstreams in both egressive and ingressive forms, and a vocal-tract–generated airstream that functions only ingressive, as in a kiss. Vowels permit nearly free airflow (e.g., [e] with spread lips), whereas consonants involve obstruction or closure. These basic segments build syllables and full utterances and are overlaid by suprasegmental features—stress, loudness, pitch, length—and secondary articulation.
Perceiving and Measuring Speech: Auditory and Acoustic Phonetics Auditory phonetics examines the ear and brain to determine which parts of the speech signal humans can perceive and how speech perception operates. Acoustic phonetics analyzes the physical properties of speech—such as frequency patterns and friction noise—using instrumentation. Background noise and anatomical or physiological differences between speakers complicate straightforward analysis and shape the overall signal. These branches are pursued in an interdisciplinary way alongside psychology, anatomy, acoustics, and physiology.