An obstruent is a class of speech sounds, primarily consonants, characterized by an obstruction of the airflow in the vocal tract that is sufficient to cause a significant increase in air pressure above the point of closure or constriction. This obstruction results in either a complete blockage of airflow, or turbulent airflow (friction).
Characteristics
Obstruents are defined by several key phonetic and phonological features:- Airflow Obstruction: They involve a substantial impediment to the passage of air through the vocal tract, which differentiates them from sonorants.
- Pressure Build-up: The closure or narrow constriction leads to a build-up of air pressure behind the obstruction, which is then either released abruptly or allowed to escape turbulently.
- Non-Sonorous: Compared to sonorants (such as vowels, nasals, liquids, and glides), obstruents have lower relative sonority. This means they are less vowel-like and do not typically form the nucleus of a syllable.
- Voicing: Obstruents can be either voiceless (produced without vocal cord vibration, e.g., /p/, /s/) or voiced (produced with vocal cord vibration, e.g., /b/, /z/).
- Sound Source: The primary source of sound for obstruents is often the turbulence created by the obstruction itself, or the sudden release of built-up pressure, rather than primarily the vibration of the vocal cords.
Types of Obstruents
The main categories of obstruent consonants include:- Stops (Plosives): These sounds are produced by a complete closure of the vocal tract, blocking airflow entirely, followed by a sudden and explosive release. Examples include the voiceless stops /p/, /t/, /k/ and the voiced stops /b/, /d/, /g/.
- Fricatives: These sounds are produced by creating a narrow constriction in the vocal tract, through which air flows turbulently, generating a noisy friction. Examples include the voiceless fricatives /f/, /s/, /ʃ/ (as in "shoe") and the voiced fricatives /v/, /z/, /ʒ/ (as in "measure").
- Affricates: These sounds begin as a stop closure and are immediately released into a fricative at the same place of articulation. Examples include /tʃ/ (as in "church") and /dʒ/ (as in "judge").